this is the same one on newegg.
i wouldnt suggest that PSU, i would either go with Antec, OCZ, Corsair, FSP, Silverstone, PC Power and Cooling, and i forgot a couple...
Reason is because it has high efficiency, and protects your systems if theres anything like overload, short circuits, etc.
Im guessing that you dont want ATI?
I think the 4850 is better than the 9800GTX, and I think nVidia then released the 9800GTX+ that has higher clocks to compete with the 4850. I could be wrong, so dont take me up to it.
Though i know the 4850 is better than the 9800GTX+ from a few posts i have been reading.
With the 9800GTX you need 2 X 6 pin PCI-E connectors, while with the 4850 you only need one. Might want to think about that.