MrZucchiniHead plays with a p41.6 I believe and a pci card and it plays it fine. I have played it with onboard 6100 and it also plays it fine. You might need to run a custom autoexec.cfg file to turn a bunch of crap off that rob's frame rates. cassie's config for cal is a good starting point.
I have a pci 6200 as my backup card. It only gets ~600 in 3dmark05 with my 2.53ghz amd and 1gb ram (I've seen the pci-e versions do much better but pci is restrictive). Also I think it wouldn't even play FEAR. But its just a temp card that I haven't even used in a year and I might of just not set it up right.