I wouldn't think so. I can run 1680x1050 with 8xQ AA settings (physx off) at (mostly?) 60 fps with a 5850, and I have a stock speed core 2 duo 2.0 GHz e8400. What is your CPU, what OS, and have you updated your video card drivers lately? What framerates are you getting?
*edit* Well, when I first installed it like a week ago I thought I got 60 fps, and now I get like 24 fps. I don't know what causes that but it's weird. Maybe my 5850 is dying already. I'll see if a reboot fixes it.
*edit again* I didn't even reboot. Two notes: One, alt-tabbing out of the game seems a little weird, so you might not want to do it too much. Two, and I think this is the big one, check your CCC settings:
Even though it says to use application settings, make sure that your AA is changed to "Box". Mine was changed to Edge, and I guess it was trying to do high-quality AA which was killing the performance. Now I get 30-60 fps in most areas it seems, and I think it still looks decent to me:
If someone thinks there's anything wrong with that image, please let me know so I can try to fix my system.
*edit one last time* Yes, using anything but "box" definitely kills my performance. I do recommend changing the AA mode to adaptive multi-sample anti-aliasing, though. There are still jaggies ingame, I guess, but it seems to make rails look better at a distance.