600~ ish build

Its a very cheap build. And i would seriously question that motherboard. But it would suit the purpose. The 955 is a good choice

Only other thing that i really see a problem with is that PSU.

Also, the 7750.....Bad card. You'd be better with a 6850/6870

You have created a build that is set up to explode!

 

That motherboard will never handle a 125W TDP processor safely so long as it's equipped with a failure-prone 3+1 phase VRM system as with many other lower end MSI AMD motherboards.  Avoid it entirely.  Look for a GA-78LMT-S2P (ask for a rev 3.1 when you order) in its place for about the same price.  Actually, your board choice is not even rated for 125W TDP processor, making your configuration impossible to run.  You will get a no POST upon first attempt to run it.

EDIT: I see it is a 95W TDP 955 but you should STILL avoid using it with that motherboard!

 

With regards to competitive options, the Antec 300 (Illusion) Is a terrible deal and will remain so if the price doesn't change.  The NZXT Source 210 has all the advantages at less cost.

you need a cpu cooler. i would get a hyper 212.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103065

For your build, I highly recommend that you wait about 1-2 weeks for the launch of the new AMD Trinity second-gen APU.

 

Given that the PC budget is under $500 for the tower, a high end AMD APU PC with the second card (6670?) in Hybrid CrossfireX represents the most appropriate option at this budget instead of a build on Socket AM3(+).  You could build a Llano APU (first-gen APU) PC with the 6670 right now but if you wait, Trinity APU launches in 9 days.  You will be able to get better performance for the price if you do.  Trinity APU is Socket FM2 which will not be compatible with Llano's FM1.

Here's a build for you. Since you're gaming, especially with an emphasis on games that can't utilize more than 4 cores, you can save money without losing performance by going for an Intel i3 (unclockable, but performance equivalent to overclocked AMD phenom IIs for less).

CPU - i3-2120 + DVD burner combo ($131)
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.936669

Cheap H61 mobo ($44 AMIR)
http://us.ncix.com/products/?sku=66933&vpn=GA%2DH61M%2DDS2&manufacture=Gigabyte

RAM - 2x4gb 1333mhz ($39)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231424

GPU: 6870 ($140 +promo code and after $30 rebate)
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150521

Case: Coolermaster 912 ($53)
http://us.ncix.com/products/?sku=55583&vpn=RC%2D912%2DKKN1&manufacture=COOLERMASTER&promoid=1018

PSU: Rosewill Green 630w ($50 after promo code)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182200
Overkill wattage, but no other good sales, so overkill it is.

SSD - Crucial m4 64gb for $90 (recommended) or 128GB for $125
http://www.newegg.com/Product/Product.aspx?Item=N82E16820148441
Normally I wouldn't recommend an SSD at this budget. But for MMOs it actually provides some in-game benefits. You'll see less loading time for new textures entering your view. Most notable in games like WoW when meeting a large band of enemy units in Alterac Valley or outside the auction house in busy cities like Orgrimmar or Ironforge. The SSD you get should be big enough to fit your MMOs, most used programs, and possibly your OS.

HDD: 500GB Seagate Barracuda ($70)
http://us.ncix.com/products/?sku=63468&vpn=ST500DM002&manufacture=Seagate&promoid=1018

Total: $617 w/64gb SSD
Note: this is a little over budget & will cost more up front because of the ~$40 rebates. But it will be a beastly MMO computer, with an SSD & a 6870 as a video card. Drop the SSD if you need to meet strict budgetary concerns. Or you can consider dropping to a 6850 video card for $130:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127673

Edit: I just realized you need a monitor too. You can free up more money for a monitor by dropping the SSD and going to the 6850. But at that point you might consider waiting to see the performance/price of the next generation AMD APUs (not released yet, dunno when, ask the AMD-focused posters).
Edited by MisterFred - 5/6/12 at 8:31pm

here is a A8 4 core hybried crossfire soild board and a 22inch monitor all for 622.00

misterfreds build is far better