Oh, then that makes it a little more simple.
Search for prices of these cards: nVidia 9600GT/9600GSO and ATI 4670/3870. These cards should be enough for any 17" monitor IMO. The 9600GT and the 3870 are a little better, but close to the others.
Also, i looked up your PSU and should handle any of those cards with no problems at all.
Anyway, if you find a 8800GT/9800GT *really* cheap, get one of those instead.