Let us know how it runs on that system. You should have a decent chance. I have a 5850 and an e8400, and though it may not be the best looking game ever, it does seem to run great for how good it looks. I imagine that the shaded style may have helped their performance out by not requiring high polycounts or something (plus I wasn't running any anti-aliasing).I wish there was a PC demo. I don't know if my old PC is capable of running it smoothly. I have a 9800GTX+ and a Q6600, and I play at 1440x900.
edit: I open Steam and, holy shit, suddenly there is! Downloading now~