Hello, What speed is your X2? Also your PSU is plenty. I've ran a 8800GT 512 off a Thermaltake 500W pure power(Two 12V rails, one 14A, the other 15A), and I'm running it just fine with even a 4870 1GB, so you PSU should be good. I would upgrade to 3~4GB of RAM since that will make a noticeable improvement.
Edit* Also, there is no 9800GT I know of that needs 2 PCI power connectors. In fact, I recently installed one in a customers computer without any power connector's on it at all. ala a 'green' version.