This is something I was just researching on my own and came across this post, so I figured I'd respond with what I cam up with. Everything i have listed here is from newegg.com. All but two items have free shipping right now as well. I hate paying for shipping so that did factor in to some of my choices, but not many really. There is also a $30 mail in rebate on the video card, so that'll help a little, but the final price doesn't take that $30 off.
I went with the antec case here because first off I have had no problems with any of the antec cases I've done builds with and I know antec makes good psu's. This case comes with the Antec EarthWatts 500 psu which is 80+ certified as well. That psu alone is $90 on newegg. I have worked with older models of this case as well and it's not bad at all. I'm also an nvidia fan so that's why I went with the 8600GT which should be able to handle that game fairly well. If you wanted to go a little better with the graphics, I'd say to go with an EVGA 8800GTS that newegg has for $150 with a $30 mail in rebate taking it down to $120.
Here is the link to all of the items listed below.
https://secure.newegg.com/NewVersio...ishListNumber=6462925&WishListTitle=Budget+PC
Budget PC
1 Antec Sonata III 500 Black 0.8mm cold rolled steel ATX Mid Tower Computer Case 500W Power Supply - $129.95
1 MSI P6NGM-L LGA 775 NVIDIA GeForce7050 / nForce610i Micro ATX Intel Motherboard - Retail
$49.99
1 EVGA 256-P2-N751-TR GeForce 8600GT 256MB 128-bit GDDR3 PCI Express x16 SLI Supported Video Card - Retail
Mail-in Rebate $30.00 After rebate price $49.99
$79.99
1 Intel Pentium E2180 Allendale 2.0GHz LGA 775 65W Dual-Core Processor Model BX80557E2180 - Retail
$71.99
1 G.SKILL 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory $44.99
1 Seagate Barracuda 7200.10 ST3250410AS 250GB 7200 RPM SATA 3.0Gb/s Hard Drive - OEM
$64.99
1 Microsoft Comfort Curve 2000 B2L-00047 Black USB Ergonomics Keyboard Mouse Included - OEM
$21.99
1 LITE-ON 20X DVD±R DVD Burner with LightScribe Black E-IDE/ATAPI Model DH-20A4H-06 - OEM
$29.99
Subtotal: $493.88 +$14.01 shipping = $507.89