First computer build, need advice

[gamer1000k]

I'm building my first computer and I need some advice. I have done some research and come up with a list of parts for a gaming rig.

Thermaltake Tsunami Case
Ultra X-Connect 500W PSU
Asus A8N SLI Deluxe mobo
AMD 4000+ San Diego cpu
Corsair Twinx XMS 3200XL 2x512MB RAM
6800 GT gpu (can you recommend a specific manufacturer?)
2x 74GB WD Raptor Hard Drives (RAID 0)
Plextor SATA DVD+-RW PX-716SA burner
Zalman CNPS7000B-AlCu LED CPU Fan
Zalman ZM-NB47J chipset heatsink
ARCTIC COOLING NV Silencer 5 (Rev. 2) Ceramic VGA Cooler

Please post your comments and/or advice about this hardware. I am especially confused about all the different video card manufacturers. How much of a difference does the manufacturer actually make in video card performance?

 

[imported_Kensai]

Get an XP-90 with a panaflo instead of the 7000AlCu, or get the full copper version.
Get a different PSU, the Ultra PSUs are too weak. Maybe Seasonic, Antec or Enermax.

For the VGA, go MSI, Leadtek or BFG.