[Sardtok]

If you check in your BIOS you can easily see what speed the AGP slot is running,
as you can change this in the BIOS, you can also change other settings like read and write settings (these things can often be changed in the OS too, for instance through the ATI Catalyst Control Center - which Thomas so nicely pointed out is puke - takes ages to load, and the "fancy" GUI is nasty)...
I can also recommend the 9800pro, although the x800 should be pretty cheap these days I got the 9800pro to up my fps in CS Source, now if only my computer had decent parts except for the graphics card and dvd burner, then I'd be a happy man. ;)

I haven't tried running dual monitors on my 9800pro, but it's supported, and should work well...
Problem about running games on your computer would be the CPU though, most games won't run well with a 1 GHz(not GB, unless you have some cpu with insane amounts of cache) CPU...
I have a 1.4 GHz Thunderbird (AMD K7 prior to the K7 XP generation), and although a lot of games will run, they are usually quite lacking in performance due to the slow CPU...