Does the X800 series come in AGP? If so, get one of those. I'd strongly suggest for you to upgrade your motherboard with a PCIe slot. AGP is being phased out really quickly.
Grab a x800 pro its what i have and its like more than twice as fast as the 9800 pro 128 mb. I had the 9800pro then got a x800 pro and it was awsome, I paid $420 back when it came out a year ago and now its like $200 bucks go figure.