If your GPU is worth as much as your CPU, this is true for items under $200 (generally. I just made this up)
Derick folds on a SR-2 with ES Xeon chips netting him 100k PPD, and a 4P AMD G34 Server that nets him 500k+ ppd.
The best GPUs get you what ... 20k ppd? Derick's putting out 600k + easily.
TL:DR GPUs suck, get a 4p.