If overclocking in addition to twin GFX, look for XFX Black Edition, Antec CP or SG series, Corsair HX series.
If OC'ing with single GFX Corsair TX, Antec TP or EA series
If not OC'ing and single GFX any half way decent CPU incl. one you have will serve well.
I will be using a ATI 4870 untill the new 6890's come out then i will get one of those and i want the HAF 932 because i am thinking mabye in the future i will want to water cool but untill then i want the quietness of the case with all those huge fans. if you know any good quiet cases then please tell me and i will think about them they do not need water cooling capabilities i would still consider them.
With crossfire involved i think i might in the furture but not for a LONG time so i dont need a crossfire PSU
With OC'ing i will OC the cpu but not my 4870 when i get a 6890 i will OC it.