CPU/GPU gaming combo for gaming

Kind of possible.. I can fit in an i3 and a 7770 into an extremely tight budget, but the quality of the mobo and psu are not the best. And it will play most games in med/high settings at 1080p.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i3-3220 3.3GHz Dual-Core Processor ($114.99 @ Amazon)
Motherboard: MSI B75MA-E33 Micro ATX LGA1155 Motherboard ($56.99 @ Mac Mall)
Memory: Kingston Value 4GB (2 x 2GB) DDR3-1333 Memory ($26.47 @ NCIX US)
Storage: Seagate Barracuda 500GB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Amazon)
Video Card: Sapphire Radeon HD 7770 GHz Edition 1GB Video Card ($94.99 @ Newegg)
Case: MSI TC- (Black) ATX Mid Tower Case ($19.99 @ Microcenter)
Power Supply: Logisys 480W ATX12V Power Supply ($13.98 @ Outlet PC)
Optical Drive: Samsung SH-224BB DVD/CD Writer ($15.98 @ Outlet PC)
Total: $393.38
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-03-16 23:40 EDT-0400)

$400 is a very low budget, especially to expect to play on "Ultra," unless your monitor resolution is only 1366x768.
"Any" video card can go with a HD3220; the question becomes "what can you afford?" Also, what future upgrade plans might you have?
The following is perhaps the cheapest Intel system I could build, using parts I'd consider buying myself:

Intel Core i3-3220 Ivy Bridge 3.3GHz LGA 1155 55W Dual-Core Desktop Processor ...
Model #:BX80637i33220
Item #:N82E16819116775
$129.99 $129.99
You've specified this already. I would not go any lower than this.

Antec VP-450 450W ATX 12V v2.3 Power Supply
Model #:VP-450
Item #:N82E16817371045
$49.99 -$10.00 Instant $39.99
You "could" get a 350W Basiq here, but you'd only save $10, and chop off any upgrade potential right from the outset.

ASRock B75M-DGS R2.0 LGA 1155 Intel B75 SATA 6Gb/s USB 3.0 Micro ATX Intel Motherboard
Model #:B75M-DGS R2.0
Item #:N82E16813157362
$54.99 -$5.00 Instant $49.99
In addition to the PCIe slot for the video card, this board only has a single PCI expansion slot. At least it has SATA 6Gb/s and USB 3.0, but it is otherwise very limited.

Athena Power CA-GSB01DA Black 0.8mm SECC Steel ATX Mid Tower Computer Case - OEM
Model #:CA-GSB01DA
Item #:N82E16811192289
$29.99 -$7.00 Instant $22.99
This case is made with much thicker metal than is typical of cheap cases, and really looks hard to beat for the price.

HIS iCooler H775F1GD Radeon HD 7750 1GB 128-bit GDDR5 PCI Express 3.0 x16 HDCP Ready Video Card
Model #:H775F1GD
Item #:N82E16814161403
$99.99 -$10.00 Instant $89.99
A HD7750 is all your current budget can afford. It will allow you to play any game, most on "decent" settings, but nowhere near "Ultra."

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
$28.99 $28.99
8GB would be nice, but on a budget this will have to do.

Western Digital WD Blue WD5000AAKX 500GB 7200 RPM SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive - OEM
Model #:WD5000AAKX
Item #:N82E16822136769
$79.99 -$20.00 Instant $59.99
Meh. As good as you'll likely find for the price.

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

Subtotal: $439.92

Even that goes over budget, and does not include Windows, keyboard, mouse, speakers, or monitor. Do you have all of those?

I don't know of a video card that would be best. But unless you are going to drop $400 on the GFX card alone, it won't make a big difference.

$400 for the system is a bit too tight. You will want 8 gb RAM. The CPU is a chunk of the $400. Then you have PSU + case that is another $70 for a budget system just to hold and power your system.

I don't know enough about gaming gfx requirements to give you an answer but my guess says you won't be able to play those games with a $400 budget.

Feeblepenguin did a nice shopping job there, EXCEPT the Logisys PSU-shaped object. It should not be connected to computer components if there is any chance it will be plugged into an AC power source at the same time. Best described as a firecracker with an uncertain fuse, you want nothing to do with it.
Still, note that by buying from multiple sources, and playing the rebate game, you can get some slightly better parts.

Onus has hit the nail on the head.

That is about the best system you are going to get for the money. You can experience the games but you might not enjoy them.

Perhaps try to get a system board you can upgrade in the future for cheap. For example in the future you could put a couple SLI cards in a system as the good cards now go down as the nex gen stuff enters the market.

If there is a Microcenter near you, they often have some very good instore-only deals, like CPU+mobo combos. Most if not all of their better deals require you to go to one of their stores though, and of course you will pay extortion (sales tax) on instore purchases.

For ~$400 what parts are you needing?

Intel version:
* i3 3220 is about $115-120, otherwise you should be looking at a Pentium 860 for about $70
* z77 mobo if you want OC'ing in the future on a different CPU, otherwise H77 for a bit less (~$10-20) or even B75 for bit less than H77.

AMD version:
* PhII x4 955/965 CPU for about $100 or Athlon II x4 640 for about $70 for this budget range.
* 970 based mobo to keep costs down

Intel build over budget, but would need to reduce GPU down to fit within $400 budget:

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Pentium G860 3.0GHz Dual-Core Processor ($68.98 @ Amazon)
Motherboard: MSI B75A-G43 ATX LGA1155 Motherboard ($67.50 @ Newegg)
Memory: Corsair Vengeance 4GB (2 x 2GB) DDR3-1600 Memory ($34.99 @ Amazon)
Storage: Seagate Barracuda 500GB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Amazon)
Video Card: Sapphire Radeon HD 7850 1GB Video Card ($154.99 @ Newegg)
Case: Zalman Z5 ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: Antec 450W ATX12V Power Supply ($36.17 @ Amazon)
Optical Drive: Samsung SH-224BB DVD/CD Writer ($17.99 @ Newegg)
Total: $460.60
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-03-16 23:52 EDT-0400)

AMD Build, same as above, but with AMD CPU/Mobo:

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD Athlon II X4 640 3.0GHz Quad-Core Processor ($69.99 @ Amazon)
Motherboard: Asus M5A97 LE R2.0 ATX AM3+ Motherboard ($79.99 @ Newegg)
Memory: Corsair Vengeance 4GB (2 x 2GB) DDR3-1600 Memory ($34.99 @ Amazon)
Storage: Seagate Barracuda 500GB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Amazon)
Video Card: Sapphire Radeon HD 7850 1GB Video Card ($154.99 @ Newegg)
Case: Zalman Z5 ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: Antec 450W ATX12V Power Supply ($36.17 @ Amazon)
Optical Drive: Samsung SH-224BB DVD/CD Writer ($17.99 @ Newegg)
Total: $474.10
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-03-16 23:54 EDT-0400)

If you drop the GPU down to 7770 GPU (~$110) you would save about $45 off of builds above:
HIS iCooler H777F1G2M Radeon HD 7770 GHz Edition 1GB 128-bit GDDR5 PCI Express 3.0 x16 HDCP Ready Video Card

I wouldn't recommend any Logisys PSU. They are generally not worth the $ for them, IMHO. I'd stick with quality PSU's from Antec/Corsair/Seasonic/PCP&C/XFX if I was buying.

Here. I replaced the "Logisys PSU-shaped object" with a more reliable antec psu. Also, a good upgrade would be to go for 8 gigs of ram, but 4 gigs will suffice probably.

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i3-3220 3.3GHz Dual-Core Processor ($114.99 @ Amazon)
Motherboard: MSI B75MA-E33 Micro ATX LGA1155 Motherboard ($56.99 @ Mac Mall)
Memory: Kingston Value 4GB (2 x 2GB) DDR3-1333 Memory ($26.47 @ NCIX US)
Storage: Seagate Barracuda 500GB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Amazon)
Video Card: Sapphire Radeon HD 7770 GHz Edition 1GB Video Card ($94.99 @ Newegg)
Case: MSI TC- (Black) ATX Mid Tower Case ($19.99 @ Microcenter)
Power Supply: Antec Basiq 350W ATX12V Power Supply ($25.74 @ Amazon) See note below.
Optical Drive: Samsung SH-224BB DVD/CD Writer ($15.98 @ Outlet PC)
Total: $405.14
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-03-17 00:06 EDT-0400)

Here. A reliable psu with a 6pin connector. http://www.newegg.ca/Product/Product.aspx?Item=N82E16817182074

Sorry to be a nitpicker, but that PSU doesn't come with a PCI-e power connector (6 pin for that GPU), so I wouldn't recommend it, but it is at least better than the Logisys that was used earlier

If you want a decent performing PC for 130 bucks go with the AMD FX 6300. It's a "six" core CPU and pretty decent for gaming.

As for GPU your in the 7770 range. DO NOT go any lower than this as you won't be able to play too many games at 1080p. The worst graphics card I would buy would be the 7850.

For your RAM, don't get the cheap 1333 value RAM. I know your on a budget but you can afford to spend 30 bucks on some 1600Mhz Corsair Vengeance or Kingston HyperX. Why sacrafice so much performance for literally a couple dollars.

Seriously though I would not build something for 400 dollars. The lowest I would possiblly go would be 600$. So save up some more money and don't buy a PC right now, would be my advice.

Starcraft 2 on ULTRA for $400?
Sorry, but SC2 is actually quite demanding:
http://www.techspot.com/review/305-starcraft2-performance/

Starcraft 2 is quite CPU-intensive. Regardless of graphics quality, once you get a big battle going a lower-end CPU is going to struggle and you can easily plummet to slide-show territory at times.

You really need to spend at least $600 on Hardware (Windows is another $100). The difficulty with $400 is that this is really about the minimum to build a "gaming" PC. Every $100 you have to spend over $400 results in a HUGE difference in its gaming performance. $600 versus $400 hardware isn't 50% better it's worlds apart.

Feeblepenguin's build is quite good considering it's $400 (again no Windows yet).

If you budget $600:
1) get an i5-3570
2) get an HD7870 2GB
3) upgrade the Power Supply

*When you get a solid CPU like the i5-3570K it's a little "future proof" meaning in two years you can add a much better graphics card. When your budget doesn't allow this (the best system is balanced) requiring a dual-core or lower-end quad AMD this creates major bottlenecks.

Other:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814202026
It's not in your budget, but it's interesting to note that for about $290 after MIR you can get a great HD7950 that currently comes with two games: Crysis 3, and Bioshock Infinite. Since these cost about $120 total, the actual cost of the graphics card is closer to $170! That's only about $70 more than a $100 HD7770 which doesn't have these games!

Food for thought...

Better SC2 CPU benchmarks:
http://www.anandtech.com/bench/CPU/129

Graphics card relative performance:
http://www.tomshardware.com/reviews/radeon-hd-7950-review-benchmark,3207-13.html

That is quite a low resolution (which usually puts stress on the CPU more) for that game.

Feel free to find a better benchmark that's up to date. It's just a rough guide. For other games this may be more of an issue, but SC2 gets both GPU and CPU bottlenecked at times.

When a big battle is happening, most of the CPU calculations have nothing to do with the graphics which is why they actually do both GPU and CPU benchmarks for this game. There's really a MINIMUM amount of processing you can get by with if you don't want really low frame rates when it gets intensive.

Oh I don't doubt it with the CPU side of things. Most games are usually GPU limited, but there are ones that aren't, which is part of my point. I know when most games are run at 1080p levels, the GPU is usually the main limiting factor (not all games though).