Switching from ATI to Nvidia

Wizzard

Hi guys
Been reading the forum for some time now, and got some amazing info from here. Here is my situation. Been using ATI for the last several years and I just build a new system:
ASUS A8N-SLI Premium ATX S939 NFORCE4 SLI DDR 2PCI-E16 2PCI-E 3PCI SATA RAID Sound GBLAN
the AMD Athlon 64 3700+ Processor S939 San Diego 2.2GHZ 1MB L2 Cache 90NM
I also picked up a EVGA e-Geforce 7900 GT CO 500 MHZ PCI-E 256 MB 1.5 GHZ DDR3.
2 questions :
1) My current PSU is an Antec True 430 watts with the following numbers :
DC output +5v, +12v, +3.3v, -5v, -12v, +5v
MAx 36a, 20a, 28a, 0.5a, 1.0a, 2.0a
Can i use this or do i need another PSU? And if so which one?

2) Which are the best drivers for this card? Omega or Nvidia i would like to OC it.

Thanks for the help as i am a newbi to all of this.
Wiz