Ah, I guess that 9800GT need 1x 6pin power connector from PSU.
How old your PSU?
The specs of PSU are good, but it only has 430W max. So, I think you will better with a brand new PSU, it also good for longer term. Get a trusted brand like Corsair, Antec, Seasonic, OCZ, SilverStone with 500W minimum for a single graphic card.
But if you are really just want to buy that 9800GT then 450W is enough for your need.