http://www.tomshardware.com/reviews/ati-agp-3850-agp,1939-5.html
[img:5e6b07523f]http://img507.imageshack.us/img507/1184/image015yp7.png[/img:5e6b07523f]
Asrock mobo with an AMD Athlon 64 3400+ (Venice), 2.2 GHz, 512k L2 cache
http://www.tomshardware.com/reviews/ati-agp-3850-agp,1939-3.html
I think regardless of AGP/PCIE the single core processor is holding it back in this example.  I would bet that my Pentium D (which is dual core) + X1950XT is not much better than this example... a C2D would be better than a Pentium D and C2Ds can be found for around $60 on the cheap end right now.  I don't know follow the AMD processors too much but I'd imagine it's similar.