Some benchmarks of the x850 here
http://www.xbitlabs.com/articles/video/ ... 0xl_5.html
The articles about the pci express version but the performance is the same on the agp version.
Not really sure what settings you could play on, if you want the best performance for agp money cna buy then this is what you want:
http://www.theinquirer.net/?article=30502
It'll be on sale at overclockers uk on 31st of this month for £282. That and the x850 imo are your only real options, the other 7800gs some other company brought out is crippled and not worth it.