Well eidos have released patch 1.2, which fixes some problems with the fx series of cards. It would play really shite on all of them because they cant support shader model 2.0 very well (if at all), so this patch lets Hitman support shader model 1.1. Or something like that, all I know is that it runs a lot better on fx cards with the patch.
It will run fine, as long as you dont crank up the AA etc. It WILL slow down in areas with lots of bodies though, even my 6800GT slows down in places where theres lots of people. Mainly when Ive shot them all to hell because Ive fucked up the mission though.
If you want to find it cheap, have a look on eBay. My collectors edition cost me £25 from Gamestation, and I looked on eBay a few days later and there was a (used) copy on there for £14... thats including p+p...