Yeah, depends what your motherboard can do. Most wil do 4x.....some will do 8x. Do you know what make/model your motherboard is? try running it in 4x and see if you get any improvements. Also, have you tried a benchmarking program called 3dmark 2001? I would definately recommend that program to everyone, as it will give you an idea of what your graphics card and overall pc setup is capable of. It also displays your system info in depth.
in your case rchrd, go to:
http://www.futuremark.com/download/
scroll down and download this:
3DMark®2001 Second Edition (Build 330)
it's 39mb though, so i hope you got broadband
But when you run the program, click on 1. System Info 2.motherboard info 3. AGP capabilites. This will tell yuo all about what AGP setting you can use. The program itself is good for measuring game peformance and will run a series of tests...I think we should all do this, and submit our scores here.. then we can compare each others system performance.