Help! What GPU for Budget Build???

APPROXIMATE PURCHASE DATE: Wednesday; Payday BUDGET RANGE: $500 and under ($400-450 preferable)

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: Gaming, Web Browsing, Multimedia

PARTS NOT REQUIRED: OS, Monitor, Speakers, Keyboard, Mouse, Hard Drive, DVD Drive, Aftermarket Cooler

PREFERRED WEBSITE(S) FOR PARTS: None; I chose all my parts from Newegg but I'll buy from anywhere offering the best bang for the buck.

PARTS PREFERENCES: None

OVERCLOCKING: Yes, but not to a serious degree, experimentation mainly SLI OR CROSSFIRE: No

MONITOR RESOLUTION: 1024x768

ADDITIONAL COMMENTS: I'm going to list the four different video cards I'm planning on using. Considering I'm going to be using a monitor with a low max resolution, do you think the 4670 will be good enough to play all of today's newest games (Fallout 3, Crysis, Bioshock) on max? Or should I step it up to the 4850? And out of these 3 4850's, which one has the most bang for the buck? :

http://www.newegg.com/Product/Prod [...] 6814102833
http://www.newegg.com/Product/Prod [...] 6814150351
http://www.newegg.com/Product/Prod [...] 6814161245
http://www.newegg.com/Product/Prod [...] 6814161252

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THE BUILD:

CPU/PROCESSOR: AMD Phenom II X4 940 Deneb 3.0GHz 4 x 512KB L2 Cache 6MB L3 Cache Socket AM2+ 125W Quad-Core Black Edition Processor - Retail
http://www.newegg.com/Product/Prod [...] 6819103471 ~$190

MOTHERBOARD: BIOSTAR TA790GXB A2+ AM2+/AM2 AMD 790GX ATX AMD Motherboard - Retail
http://www.newegg.com/Product/Prod [...] 6813138143 ~ $80 ($10 After -$70.00 from combo deal)

GPU/VIDEO CARD: HIS Hightech H467QT512P Radeon HD 4670 IceQ Turbo 512MB 128-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Prod [...] 6814161252 ~ $70

or

SAPPHIRE Vapor-X Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Prod [...] 6814102833 ~ $110

or

XFX HD-485X-ZDFC Radeon HD 4850 1GB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Prod [...] 6814150351 ~ $120

or

HIS H485QS1GP Radeon HD 4850 1GB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported IceQ4 Video Card - Retail
http://www.newegg.com/Product/Prod [...] 6814161245 ~ $130

CASE: RAIDMAX SMILODON Extreme Black ATX-612WEB 1.0mm SECC Steel ATX Mid Tower Foldout MB Computer Case - Retail
http://www.newegg.com/Product/Prod [...] 6811156078 ~ $80

RAM: OCZ Fatal1ty Edition 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model OCZ2F10664GK - Retail
http://www.newegg.com/Product/Prod [...] 6820227364 ~ $50

PSU: 550W Antec TruePower (Older model I have laying around my house) ~ Free

Combo Deals: http://www.newegg.com/Product/Comb [...] mbo.209473 ~ $200 (Motherboard and CPU)
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I guess what I'm mainly looking for here is which of these 4 video cards is going to give the best bang for the buck and allow me to play Fallout3 and Crysis on max settings on a 1024x768 resolution?

PRICE WITH THE with the $70 4670
Subtotal : $409.96
Shipping: $31.64
Grand Total: $441.60

Are you sure you want such a powerful cpu with a weak gpu? For gaming purposes, weaker cpu paired with stronger gpu is better especially if you overclock. I would recommend a phenom II x3 720 (140) or phenom II x2 550 paired with a sapphire hd 4870 512mb ($135). But that is if you are gaming. I realize that you are only asking for help with the gpu, but I couldnt resist.

I would chose the sapphire hd 4850 with 512mb over the others you listed, because you dont need the extra memory.