Looking for some advice on a gaming rig ($1500 budget)

[Freakin]

I'm looking to build a gaming rig for my 15 year old bro in law.

Got a budget of $1500, and I want to make sure it will be a capable machine for a while.

Currently I'm looking at

Core 2 Duo E6600
Asus P5W DH Deluxe (I'm pretty big on Asus, so I'd like to stick with them)
2GB (2x1GB) PC6400 Corsair XMS CAS 4
CoolerMaster Centurian Case

Outside of that, I'm not sure what to go for. I definitely want Nvidia over Ati.

I'm not sure if I want to go with a DX10 card or stick with a nice 7900 or 7950 setup.

Also not sure what kind of PSU to drive the video card(s).

Harddrives I can figure out my self, and no OS needed...