Need a new system for budget gaming $400

PCPartPicker part list: http://au.pcpartpicker.com/p/1nozg
Price breakdown by merchant: http://au.pcpartpicker.com/p/1nozg/by_merchant/
Benchmarks: http://au.pcpartpicker.com/p/1nozg/benchmarks/

CPU: AMD A10-5800K 3.8GHz Quad-Core Processor ($145.00 @ Mwave Australia)
Motherboard: Gigabyte GA-F2A55M-DS2 Micro ATX FM2 Motherboard ($67.00 @ PLE Computers)
Memory: Corsair XMS3 4GB (2 x 2GB) DDR3-1600 Memory ($59.00 @ PCCaseGear)
Case: Cooler Master Elite 335 Upgraded ATX Mid Tower Case ($45.00 @ Mwave Australia)
Power Supply: Silverstone Strider Essential 500W 80 PLUS Certified ATX12V Power Supply ($59.00 @ PCCaseGear)
Optical Drive: LG GH24NS95 DVD/CD Writer ($21.00 @ Mwave Australia)
Total: $396.00
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-08-02 23:35 EST+1000)

Def need an APU with at least 1600 ram to make this build possible. Dang, I feel bad for you aussies, very expensive computer parts over there!

EDIT: The CPU is an APU and comes with a GPU (graphics card)

Oh you're right i had completly missed that

As I'm sure you know, $400 is a rather sparse budget for gaming.
First of all, I saw that you are in Australia. Your prices and availability are no doubt different, but the following is an example of the kind of system you might build:

Xigmatek ASGARD 381 CCC-AD38BT-U03 Black Steel / Plastic / Metal Mesh ATX Mid Tower Computer Case
Model #:CCC-AD38BT-U03
Item #:N82E16811815018
$49.99 -$25.00 Instant $24.99
Cheap case, but sufficient.

AMD A10-6800K Richland 4.1GHz (4.4GHz Turbo) Socket FM2 100W Quad-Core Desktop Processor - Black Edition AMD Radeon HD 8670D
Model #:AD680KWOHLBOX
Item #:N82E16819113331
$149.99 $149.99
This build won't have a discrete GPU, so I chose the top APU. If you can raise your budget, a discrete GPU (more likely in an Intel build) will perform a LOT better.

ASRock FM2A75 Pro4-M FM2 AMD A75 (Hudson D3) SATA 6Gb/s USB 3.0 HDMI Micro ATX AMD Motherboard
Model #:FM2A75 Pro4-M
Item #:N82E16813157334
$74.99 -$15.00 Instant $59.99
Has modern interfaces. I've had good results from ASRock.

CORSAIR CX430M 430W ATX12V v2.3 80 PLUS BRONZE Certified Modular Active PFC Power Supply
Model #:CP-9020058-NA
Item #:N82E16817139049
$69.99 -$20.00 Instant $49.99
The MODULAR versions of the Corsair CX line are built with all-Japanese capacitors. The cheaper, non-modular versions, though also built by CWT, use some inferior Samxon capacitors. I would not put one in a gamer.

G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Dual Channel Kit Desktop Memory Model F3-10600CL9D-4GBNT
Model #:F3-10600CL9D-4GBNT
Item #:N82E16820231253
$36.99 $36.99
Four GB of RAM is light by today's standards, but on a tight budget will have to do.

Western Digital WD Blue WD5000AAKX 500GB 7200 RPM 16MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive - OEM
Model #:WD5000AAKX
Item #:N82E16822136769
$59.99 $59.99
Meh. Typical consumer drive. I use WD drives a lot, and don't remember the last time one failed in use.

Subtotal: $381.94
Once again, your prices and availability will be sufficiently different as to make this figure a rough idea at best.

I would not go with an A series APU. The graphics performance is still far less than even the lowest end graphics cards. Instead go with an Intel Celeron + HD 7750 and get much better gaming performance for the same price.

PCPartPicker is now blocked at my job, so I can't use it. Farkinob appears to have had a similar idea to mine. Oh, and I missed that you didn't need the HDD. This will probably allow a build using refllect's advice, which is correct; a discrete GPU will be better for games.

Ok, here's an Intel build. I removed the HDD this time, so it ducks under the $400, but again this is only an example, and uses Newegg due to the block I mentioned.

Fractal Design Core 1000 FD-CA-CORE-1000-USB3-BL Black Steel MicroATX Mid Tower Computer Case
Model #:Core 1000 USB 3.0
Item #:N82E16811352032
$49.99 -$20.00 Instant $29.99

ASUS P8B75-M LX PLUS LGA 1155 Intel B75 SATA 6Gb/s USB 3.0 Micro ATX Intel Motherboard with UEFI BIOS
Model #: P8B75-M LX PLUS
Item #:N82E16813131887
$69.99 $69.99
You can only go a little cheaper here without giving up modern interfaces like SATA 6Gb/s and/or USB3.0, which I don't think is worth it.

SAPPHIRE Radeon HD 7750 1GB 128-bit GDDR5 PCI Express 3.0 x16 HDCP Ready Video Card (11202-00-20G )
Model #:11202-00-20G
Item #:N82E16814102969
$99.99 -$5.00 Instant $94.99
Here in the US, you can find a HD7770 for only a few dollars more. If that's true in AUS, grab it, because it is a LOT stronger.

Antec EarthWatts Green EA-380D Green 380W Continuous power ATX12V v2.3 / EPS12V 80 PLUS BRONZE Certified Active PFC Power ...
Model #:EA-380D Green
Item #:N82E16817371033
$59.99 -$15.00 Instant $44.99
I listed the Corsair in the other one for the sake of modularity, but this one is actually my standard "goto" PSU in budget builds. I haven't had one fail in years.

Intel Pentium G2020 Ivy Bridge 2.9GHz LGA 1155 55W Dual-Core Desktop Processor Intel HD Graphics BX80637G2020
Model #:BX80637G2020
Item #:N82E16819116886
$69.99 $69.99
This is probably the second thing (after the HD7770) I'd improve with more money in the budget; a hyperthreaded i3 could make a huge difference in newer games.

G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Dual Channel Kit Desktop Memory Model F3-10600CL9D-4GBNT
Model #:F3-10600CL9D-4GBNT
Item #:N82E16820231253
$36.99 $36.99
In a budget build, 4GB will have to do.

LG 24X DVD Burner - Bare Drive Black SATA Model GH24NS95 - OEM
Model #:GH24NS95
Item #:N82E16827136259
$17.99 $17.99
Meh. One optical drive is much like another.

Subtotal: $364.93

This silliness can only be the result of a misunderstanding; without a GPU there is no way an i5-3570K with its HD4000 is going to play Crysis 2 in Ultra; I'd be surprised if it hits Medium, but would be happily corrected.

What resolution? That is indeed interesting. Really. It actually supports my own sentiments that it doesn't take a $400 graphics card to play games. My own builds, until recently (I have spent more lately on graphics cards) always favored more powerful CPUs.

Interesting indeed.
Still, with a $400 budget, I'm not sure you'd fit even the i5-3570K (has the same HD4000 graphics) into the build, especially with a PSU large enough to support a hefty graphics card later.

Well, he doesn't need the HDD, but he's in Australia, so no Microcenter deals.
Also, 2x2GB of RAM will give better performance than 1x4GB; the latter might be appropriate on a board with only two RAM slots, with the intent to upgrade without replacing anything.

Ok, but an ATX board typically has 4x RAM slots, so a 2x2GB kit would be ok and he wouldn't need to replace anything.

Funny.
I should probably test my HD4000 graphics on some of my games. From looking at some game review articles though, games like GW2 should probably only run on low settings.

No, I never did; I always had a graphics card on hand. The weakest card I tried to use with GW2 was a HD6670/GDDR5 at 1600x900. Some better settings were grayed out, and it was a little jittery, but not unplayable. Still, a HD7750/GDDR5 was a lot better.

I think the suitability of using an IGP is very applicable to the topic. If HD4000 is sufficient, not needing to buy a graphics card will improve performance in other areas, particularly the CPU. There could be some severe trade-offs though, depending on AUS pricing and availability. An i5-3570K is a pretty big chunk out of the budget.
What do you think, Jaidev, can you fit an i5-3570K and even a H77 mobo + RAM into your budget?

At that budget, as others have said, you're definitely better of sticking with an integrated graphics solution and spending more on the CPU and other components. Then if you have more money later on you can get a dedicated graphics card and will not have shortchanged yourself on the CPU said while still being able to play games at medium settings at 1080p.

The two most important pieces to consider if you move forward with that strategy is the CPU and power supply. Make sure your power supply is capable of handling a dedicated GPU later on. 550-650 watts should be plenty depending on what GPU you get later on.

H77 because of price. He's getting the 3570K for the IGP, not because it can overclock. Technically, he could even get a H61, but I think that's too cheap to go on the mobo, since it either won't have modern interfaces, or they'll be added by [slow] 3rd-party controllers tacked onto it.
Depending on AUS prices, I'd have to wonder if i3+HD7750 isn't cheaper than the 3570K.

A hyperthreaded i3 is a pretty good CPU for games, and might allow the purchase of a discrete GPU that's better than the HD4000. For example, using Newegg prices, an i3 I think is only $110 (with a code), and you can get a HD7750 for $90-$95. OTOH, a 3570K is still $220. At this point it really depends on what AUS prices are like.
I'd think that for games, an i3+HD7750 would be a better choice than the i5-3570K with its HD4000 IGP, so that's why I mentioned it.