cedega should allow you to play most games under ubuntu (except for those requiring SM3.0, like crysis and bioshock)
nvidia's recomendation isn't exactly what's necessary. a higher end 550W unit would do rather well(assuming he's running a c2d or c2q, only 4 sticks of RAM and no more than 3-4 harddrives) I'm running 4GB RAM, 3 harddrives, a 640mb 8800GTS and a 3.6 Ghz c2d on a 400W unit though admitedly i probably don't have much extra headroom
