In order for him to have 2 GFX (Nvidia 6800 ultra) connected using SLI tech he must have a motherboard that supports it, which he doesn't ... that means buying a new comp
However, you can get the 6800 Ultra Extreme version, which is slightly faster than the ultra.
Regarding Radeon, the X850 "##" (something) should be also available soon, correct me if i am wrong.