Hasta La Motion!

Hi guys, I know all about it being discontinued and so on, well I recently got hold of shake 4.1 and would like to know what would be the ideal Mac System setup would be to run shake 4.1? All I will be doing is to match up 3D elements onto live action plates, not sure if I would be doing roto or grading as I’m going for a 3D job not a 2D.

I don’t think I can afford a Mac Pro but I have looked at the imacs and mac mini being the cheapest. However the mac mini spec is pretty limited with only 2GB Ram (upgradable), would that be enough with all the render passes and live plate that need to be comp? Also the CPU is 2.4GHz Intel Core 2 Duo, is this fast enough? Of course on the other hand the cheapest imacs have i5 CPUs now and 4 GB ram but is this overkill? I guess I just want a reliable machine to run shake and comp out a sequence of images to be edited. Any thoughts and help welcome thank you.