I use my 4p as a net-render for c4d with vray from time to time. (actually quite rarely. folding gets in the way)
It hauls the mail pretty well. cinnebenches at around 34. Are you rendering static images or with realflow or the like?
And i see no reason why you don't have three intel 12 core 3.5gigglehurtz 4ps. one to fold on, one to render, and one to keep you warm.