C4D performs excellently on my 8-core Mac. I think the CineBench scores were over 5 times those on my dual G5. The 8-core uses the X1900XT card — middle of the three offered, if I recall.
Beyond that, it integrates well with AE.
Now don’t get me wrong about what I’m about to say. You have a lot of questions about C4D, but this is an AE forum, as you know, and it would be less than useful if it were to be filled with non-AE threads. I recommend you go to the Cinema4D COW forum, C4Dcafe, or CGTalk to find out more non-AE concerns about C4D. 🙂