Are you going to be using the psu in your sig? I have a Corsair HX620 atm which may be enough for the job but I have ordered a HX1000 to make sure I have the extra headroom needed to overclock the 5970, I will also be upgrading the rest of my rig in Jan/febbto i7 but would like to see how my Q6600 copes first.
Yes, I plan to use the Enermax 625w ... ready to upgrade if necessary though - like you I am planning on a change soon, but this will do for starters! Power at wall socket for my rig (in my sig, GTX is @ 675, 1050, 1455) is:
Windows Desktop - 155w, Prime 95 small FFT - 294w, Furmark - 325w, P95 + Furmark - 468w
So, if I assume that the PSU is 85% efficient (bit optimistic!), actual power supplied is:
Windows Desktop - 135w, Prime 95 small FFT - 256w, Furmark - 283w, P95 + Furmark - 407w
So I reckon there is enough left, even with the Q6600 running P95 I have (in theory!) about 369w left to use up ... I seriously doubt I'll use all that up unless really stress testing the CPU & GPU at the same time with a good overclock on both .... fingers crossed, It will certainly be OK on stock clocks I reckon. The PSU has the appropriate connectors along with 3x25A rails for 50A combined so here's hoping ... if not then my kids gets the Enermax along with the GTX 260!