For a PC ...I'd say a 4 or 6 core processor and at least 8 gig of ram. Don't skimp on cooling fans or your video card. And I'd suggest a 600 watt power box. You'll need Windows 7 to handle the 64bit and additional ram over 3.5 gig. I don't know much about the Windows 8 to either suggest it or nix it.

For a MAC system someone else will have to post their thoughts and recommendations.