Originally Posted by holograph

cpu/ram/video ram don't effect mining.

all you need good GPUs and enough power/cooling to OC them to get good hashing rates...
I have 2 ATI 5830 which give total 550MHash/s and unless I add another 500+ MHash its not worth much mining atm unless price per BTC shoots over $20-25

get on the mining forum, there's lots of great advice

before investing in hardware study links in my first first reply here, to get good idea what to expect and keep in mind difficulty resets every 10-14 days and been going up constantly so you will have to account for that too, good thing increase of difficulty is slowing down atm, maybe we'll see decrease soon, just don't bet on it