We’ll the more cores the better, especially now that AECS3 supports multi-processing but the key is RAM, you need to throw loads of it at AE to get the most out of all those cores. My suggestion is go for a 4 core and put at least 4 GB ram in it, with more if you can stretch it. No sense having 8 cores if they just sit there idle.
JD
John Dickinson
Motionworks
http://www.motionworks.com.au