One last thing dont buy an expensive power supply. 9800gt run fine at 400 watt.
Try Cooler master 460watt or 500watt extreme plus PSU. Enough for 9800gt, also cheap too.
It's one thing to go inexpensive, but never
go cheap on a PSU. Any quality 450+ watt PSU will do, watch out for sales.
Keep an eye out for Corsair, Seasonic, PC Power & Cooling, OCZ, Antec, there's bound to be one in your budget.