PC Update help :)

Doesn't matter at this point since your build has to be max $500. AMD is the solution since it's much cheaper than Intel, though I would go with Intel if you had the money.

AMD Phenom II X4 965 Black Edition Quad Core Processor AM3 3.4GHZ 8MB Cache 125W 45NM Retail Box - AMD - HDZ965FBGMBOX

$110.00 for AMD Phenom II X4 965 Black Edition Quad Core Processor AM3 3.4GHZ 8MB Cache 125W 45NM Retail Box

ASUS M5A97 AMD970/SB950 ATX AM3+ DDR3 2PCI-E16 2PCI-E1 SATA3 USB3.0 Audio CrossFireX Motherboard - ASUS - M5A97

$90.00 for ASUS M5A97 AMD970/SB950 ATX AM3+ DDR3 2PCI-E16 2PCI-E1 SATA3 USB3.0 Audio CrossFireX Motherboard

Powercolor Radeon HD 6850 775MHZ 1GB 4.0GHZ GDDR5 2XDVI DisplayPort HDMI PCI-E Video Card - PowerColor - AX6850 1GBD5-DH

$135.00 for Powercolor Radeon HD 6850 775MHZ 1GB 4.0GHZ GDDR5 2XDVI DisplayPort HDMI PCI-E Video Card

OR

XFX Radeon HD 6850 Fansink 775MHZ 1GB 4.0GHZ GDDR5 2XDVI Display Port HDMI PCI-E Video Card - XFX - HD685XZCFC

$125.00 for XFX Radeon HD 6850 Fansink 775MHZ 1GB 4.0GHZ GDDR5 2XDVI Display Port HDMI PCI-E Video Card

Mushkin Enhanced Silverline Stiletto 8GB 2X4GB PC3-10666 DDR3-1333 9-9-9-24 Dual Channel Memory Kit - Mushkin Enhanced - 996770

$45.00 for Mushkin Enhanced Silverline Stiletto 8GB 2X4GB PC3-10666 DDR3-1333 9-9-9-24 Dual Channel Memory Kit

Done, you don't need anything else. That's about $370. Plus tax, roughly $400. You may need a new hard drive if you require that. The PSU (Power Supply Unit) should be at least 500-600W for a good and clean power.

If you are doing wireless, you will require a wireless card, if not use the LAN they have on there. Good Luck.