i think it is enough, if you are only going for one card.
since the graphic card is using pci express x16, u need to make
sure ur mobo have this slot, and i tink it is powered by a 8pin or
6pin, so ur power supply must have that connection
if u do not have, must make sure that ur card comes with a 6pin
or 8pin to molex connection.
if you intend to get a 9800gx2 card, x2 means another processor,
need more power, so must check out with the person selling