When you use hypershot or alias to render they are not limited by by cores, so i would advise quad over dual.
The phenom 940 BE is the same as the 955 and the 965. They have proven to have no cold bug so overclock well and keep stable. So from the comparison tables the 940 might not look powerful but do overclock reasnably well, they could save you money and provide you with the required processing power.
Graphics don't really come into play for rendering but they do for modelling. Depending on the program i would check out the website from the manufacturer to see their suggestions. Both Nvidia and ATI are doing multi gpu's so you could buy a card that may save you money and later on buy another one.
Ram is proportional to how big your models will be and how many you will have open and wanting to have available steps to undo.
The I7 is an imense processor but very expensive from what i have found in my searches, but the 920 will push to 3.5Ghz + even on air cooling so a nice zalman cooling unit would keep it under control.
good luck
TVR, Heres to Peter wheeler and his last creationg of the Scamander.
Coventry seriously sucks....