HI PP, this all depends on the pick'n'mix parts youre about to get in the puter itself.
I'd go for nVidea personally for your Graphics.
But iClone 5 works fine in windows 8 in both the 64 and 32 bit versions.
I have an issue whereby 382 props and about the same in plants causes me unable to use the 64 bit v. but 32 bit v. works instead so easily fixed.