I just built another computer in Oct and highly recommend it. Its a dual socket 32 thread/16 core 2.4 GHz Sandy Bridge based Xeons (E5-2665s). Intel is launching the V5 Xeons (Skylake) in June so prices are plummeting on the V1's since everyone is trying to dump them. They are dirt cheat and getting cheaper (now almost half what I paid). I only paid $110 for the two processors. I already had ram, power supply and case as my FX-8120 died so it only set me back about $500. The biggest expense is the motherboard, which I bought new. It was well worth it though! It so much faster! The nice thing about the mobo I got is I can in the future (if the prices drop enough) upgrade it to 48 core Ivy Bridge @ 2.7ghz or a 40 core @3 ghz.
That is a very interesting approach. It seems like most of the guys in the Folding@Home forums believe a GPU heavy rig is the way to go. it doesn't appear that CPU's make much of a difference. Is BOINC more multi-core CPU friendly?
I know when I signed up for World Community Grid it had an option for using the graphics card, but I didn't choose that option for the older computers that I assigned to that effort. So, I am not familiar with how GPU's work with World Community Grid.