It could be pretty close. But the graphics cards on older PC's didn't take near the juice that they do now. The whole reason 1000watt+ PSU's came out was when people were looking to put the old P4's and a couple of 8800Ultra's in the same box (yes I know the 8800's came after the P4 era was over). That's about like just leaving a hair drying running full time - probably puts out just as much heat too.

But on the other hand, PIII's and the K7/K8 althons were pretty efficient. So if you're trying to compare an older K8 with something like a Ati 1600 then that would be pretty efficient. Multiple GPU's didn't used to be more than a very small niche market too.