i'm 7 years old and a million times smarter then you!!!
The 9100 PCI is probably the fastest one out there. It's an 8500 in disguise. If there's any way you can, replace your motherboard and get a Ti4200. It won't cost too much more ($130 altogether), but the system will be lots faster for gaming.
Overstock.com has ATI PCI 9100 64MB for $50.00 + $1.00 shipping...
<font color=red><b>The mind is in its own place, and in itself Can make a Heav'n of Hell, a Hell of Heav'n.</b></font color=red> John Milton, <i>Paradise Lost</i>, Book II