How is this new PC Build for music production/3d modeling (Newegg?)

Just some thoughts:

You can actually save a lot of bucks from the offered $648-bundle if you build it yourself including BETTER equipment. I made an initial parts list (very similar to the bundle) so you can compare which one would best fit your requirement:

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-4790K 4.0GHz Quad-Core Processor ($317.99 @ SuperBiiz)
CPU Cooler: Scythe Shuriken Rev. B 3 11.8 CFM CPU Cooler ($27.00 @ SuperBiiz)
Motherboard: ASRock Z97M-ITX/AC Mini ITX LGA1150 Motherboard ($95.99 @ SuperBiiz)
Memory: Patriot Signature 8GB (1 x 8GB) DDR3-1600 Memory ($37.99 @ Newegg)
Storage: Samsung 850 EVO-Series 120GB 2.5" Solid State Drive ($64.68 @ OutletPC)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($49.49 @ OutletPC)
Case: Raidmax Cobra Z MicroATX Mid Tower Case ($39.99 @ Newegg)
Power Supply: SeaSonic 620W 80+ Bronze Certified Fully-Modular ATX Power Supply ($74.70 @ SuperBiiz)
Optical Drive: Asus DRW-24F1ST DVD/CD Writer ($12.99 @ Newegg)
Total: $720.82
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-09-05 07:50 EDT-0400

The cost for all these parts is only ~$73 higher than the offered bundle. But, these parts already includes your Solid State Drive, a top-quality Power Supply (note that the Raidmax Cobra Z PSU is a low-quality unit and should be avoided at all costs), an aftermarket CPU Cooler (since you picked up an unlocked CPU used for overclocking), an DVD/CD Writer Optical Drive (if you don't have one yet), and most importantly, a mini-ATX (smaller) Motherboard with Built-in Wi-Fi supporting the faster 802.11ac (note that the bundled standard-ATX motherboard does not have wi-fi support and you are forced to buy a wi-fi adapter card to be able to connect wirelessly).

Just something to think about to maybe help you in your decision. Best of luck!

Mini-ATX or ATX?
The main features that are sacrificed in a mini-ATX motherboard are the RAM slots and the multi-GPU capability. So if the expansion you are thinking is along the lines of either 1) going for 4 pieces of memory sticks, or 2) doing SLI or CrossFire, then the mini-ATX is certainly not for you. However, if the expansion is only related to adding up more SSD's or HDD's, then most mini-ATX have that same features with the ATX boards. The main reasons for going with the mini-ATX are the size constraints (i.e., you are forced to select a small case because you require portability or you have no ample desk space for your PC), the cost (i.e., you have a very tight budget that saving a few bucks here-and-there would be good in limiting your expenses), and/or the specific use (i.e., your build will be used for none other than what is intended and expanding that same PC for other purposes is out of the question).

Comments and Suggestions on your Revised Parts List
You might want to rethink the motherboard + PSU combo you linked. The PSU, which is the 650W Cooler Master GM Series G650M, is a so-so component categorized only as Tier-3 in the Latest PSU Tier List. You would be better off in going for a power supply ranked among the top two tiers in that list. If you really want to go with the Cooler Master brand for your PSU, choose either the V or the VS series. Note that there may be other top-tiered brands/models that are more affordable than that mediocre G650M (since for your rig, you won't be needing that much power unless you decide on the GPU now).

For the motherboard, I've read that the Asus Z97-A/USB 3.1 had some poor reviews, plus it costs $140. There may be other cheaper alternative with the same features as that motherboard. The USB 3.1 is a new feature, but most devices still use the 3.0 / 2.0 port (I am not sure whether you will be able to take advantage of that feature within the next few months - might be better to factor in that feature when the time comes that motherboards have 3 to 6 ports that are USB 3.1, which means there is a demand for that port).

You might want to check the ASRock Z97 EXTREME4 which only costs $97. They both support a wide-range of higher-memory modules up to 3200MHz, with 4xDDR3 slots, up to a max. cap. of 32GB. They both are ATX format (which you said you prefer for "expansion"). They both support multi-GPU in both SLI and CrossFire. However, the main advantages of the ASRock against the Asus are the number of SATA 6GB/s ports (8x against 6x) and the quality of Audio Codec (Realtek ALC1150 vs Realtek ALC892).

I would also rethink the choice of the SSD. The Kingston SSDNow V300 120GB is ranked 530th/705 in the SSD User Benchmarks with a terrible effective speed rating. If you cannot afford the high-performance Samsung 850 EVO's, you might want to check other affordable SSD's (depending on the store you will be purchasing this from) that are more efficient than the SSDNow (such as the Crucial BX100 120GB or the OCZ Vector 150 120GB). Note that prices of these SSD differ from store-to-store, some might be cheaper in one location and some more expensive in another location.

One more thing, about the Wi-Fi Adapter, if you can get a motherboard with a built-in Wi-Fi, then, the better. Usually, built-in wi-fi's support the faster 802.11ac connectivity (aside from the slower 802.11a/b/g/n). Another disadvantage of the adapter card is you will use up a PCI or PCIe slot on your motherboard (and, consequently, an expansion slot in the back of your case) which may (or may not) hinder airflow, such as rear exhaust fan (due to protruding antennae) or interior fans of your GPU (especially if the wifi card is under the video card). So more hassle in the placement of an adapter card compared to the built-in wi-fi feature.

Also FYI, you'd need a Wireless Router that supports AC Wifi for it to work at AC speeds.

Also, don't do a 4x4 ram set. That'd only ideal for quad channel motherboard, you're only getting a double dual channel motherboard. For performance and bug/error free reasons, stick with a 2x8 kit.

You're very welcome!

Good choice on the Tier-1 PSU. Just to let you know (for additional info only), since I think you haven't selected a final GPU yet, that 650W can easily power any of these following single-video cards: [NVIDIA GEFORCE] GTX 950, 960, 970, 980, up to a 980Ti and a Titan X (but not a Titan Z), [AMD RADEON] R9 280, 280X, 380, 290, 290X, up to a Fury X (but not an R9 390X).

For an alternative ATX motherboard with wi-fi feature, there's the Asus Z97-PRO(Wi-Fi ac)/USB 3.1 ATX LGA1150 Motherboard and the Asus Z97-DELUXE(NFC&WLC) ATX LGA1150 Motherboard. The Pro version is almost similar to your originally-selected Z97-A/USB3.1, but with a better ALC1150 audio codec, 4x PCIe 2.0 x1 (instead of 2x PCIe + 2x PCI), and, of course, the on-board wi-fi included. The Deluxe version costs more than the Pro due to some added features. The main differences between the Deluxe and the Pro are: Max. RAM Bandwidth Support (3300MHz vs 3200MHz); Rear Panel PS/2 Keyboard-Mouse Port (None vs 1); Rear Panel USB Ports (10 = 6x USB3.0 + 4x USB2.0 vs 6 = 2x USB3.1 + 2x USB3.0 + 2x USB2.0) and SATA Express Connection (2 vs 1).

Note that the faster AC wireless connectivity that are featured in most (if not all) devices are backward compatible. Meaning, if you have an adapter or a router that only has an 802.11n or even the slower 802.11g, the new device with an 802.11ac will still function to the maximum speed of the slower device it is paired with. So if you only have an 802.11n wireless router, having a better 802.11ac wireless adapter will still work to 802.11n speeds until such time you decide on upgrading your router in the far future. Since we all have slow internet speeds (mind you mine is 3mbps lol), the AC connectivity works best with local networking (i.e., sharing files/folders among your devices for faster transfers). Internet speeds don't increase as it is limited by our ISP package.

Consequently, both the recommended Asus motherboards above with on-board wi-fi have receiver extensions/antenna stand which you can mount on top of your case (or on other location as far as the antennae cable can reach) for better reception. See this photo of the motherboard (note the connected extension). On the other hand, your originally-selected wi-fi adapter (I think) has no antenna extensions (the antennae is limited to its location at the back of your PC case).

Good choice on the SSD. The Samsung 850 evo is of good-quality, highly-rated, and affordable.

The G.Skill Ares and the G.Skill RipJaws X are both identical in performance. The only difference is the height of its heat spreader. The Ares is slightly lower; the RipJaws X is slightly higher. This will come into factor when using large CPU coolers that might protrude into the RAM sticks. In your case, you don't have to worry about it - just pick what's cheaper or what looks best for you.

Note that the motherboard we have discussed supports dual-channel memory. This means it works in pairs 2x2GB or 2x4GB or 2x8GB. Here's a good discussion whether you want to fill all your RAM slots or not. As long as the memory sticks you selected supports the memory speed your motherboard has (including it's maximum capacity), you will be fine. Here's another discussion thread and another one here for your additional information.

Hope these information helps!

Here are my thoughts:

1) The far left (the first one) has a higher Latency of 10 (the lower the number the faster the memory). But you won't see a noticeable difference in real-world/normal usage. All the rest are just the same. Recommendation: Pick the cheapest.

2) Part of the price you pay for Asus is their reputation/reliability in manufacturing those motherboards. It's $302.99 in Amazon, but, I found in Newegg it only costs $209.99 (not available currently though - must be out of stock). Another cheaper alternative with almost the same specs as the Asus is the ASRock Z97 Extreme6/ac ATX LGA1150 Motherboard ($212.41 @ Amazon). Recommendation/s: Get that Asus from Newegg if it's on stock. Get the ASRock if you really really want to buy now.

3) You don't "have" to pick the most expensive among those 650W EVGA PSU's. You just have to make sure that the model you are choosing is one of the more reliable, efficient, and safe.

The P2 Series (at the far right), which is the most expensive, is rated as Tier-1 (most stable and highest quality) in the PSU Tier List. The P2 also has an efficiency rating of 80+ Platinum, ideal for those who usually run their PC's 24/7 (or close to that). The 80+ Platinum effectively decreases the monthly/annual electricity cost of your system.

The G2 at $96.50, is also rated as Tier-1. It has an 80+ Gold efficiency rating that is a little bit lower than the Platinum. It is still advisable for the 80+ Gold to be used for such 24/7 PC's. Both the P2 and the G2 were manufactured/supplied by Super Flower (a renowned PSU manufacturer).

The GS at only $69.99 is rated Tier 1 and has the same quality as the G2 series, with only a slight different of providing less than 0.1A at the +12V rail. The GS is manufactured/supplied by Seasonic (another renowned and reputable PSU manufacturer).

The cheapest in your list is the NEX Series, which is categorized as Tier-4 (poor-quality components). That NEX is supplied by FSP Group (an average or so-so PSU manufacturer).

Recommendation: Get the more-affordable but high-quality GS Series (the third one in your link).

4) For the first warning, you must select a lower RAM speed as the 2400MHz requires a 1.65V to operate. The CPU you selected is recommended to perform at a 1.5V only. The 2400MHz may still work the speed on overclocking but it's risky if you don't know much about setting correct voltages (over-voltage might fry your component). Recommendation: To be safe, select a 1866MHz that's enough for 1.5V.

For the second warning, it only means that pcpartpicker has not yet verified if the height of the CPU Cooler will fit in that case you selected. You have to verify manually the interior clearance of that case so that the top of the CPU Cooler will not hit the case's left side panel when installed. According to this review of the Rosewill Galaxy-01 Case, it has a CPU Cooler actual clearance of 160mm. The Cooler Master Hyper T2 or the Blizzard T2, according to their website (Hyper T2) and according to this website (Blizzard T2), has a total height of 140mm. Recommendation: Ignore the pcpartpicker warning as the CPU Cooler will fit in your case.