You would be under limit. Least power supply needed for standard 9800GT is arround 400W which can provide at least 18amps of constant current. This would mean that you need to go with good, branded PSU of 350W+. In my opinion it would be best to buy something like Corsair CX430, Antec 380 or if wan't something cheaper Cooler master Elite 460W. So, unload about 20-25$ more for one of these and you'll be good.