If you have the money, I would go with an i5 2500k for gaming and a Xeon build with ECC memory (for reliability / error checking) and a Workstation card, specially if is related to your actual work. Otherwise, I would go with in i7 2600k build for a system capable of doing both but being the better gaming system.
So go with my i7 build and my GTX570?
I still have my Dell XPS 420 with the q6600. Should I turn this into a 3D animation, design machine? Should I add a quadro card to it?