The Intel Gigabyte manuals say that a 4 pin plug is sufficient for CPU's up to 120 watts. So for anything other than an EE chip, you should be OK.
(A Q6600 OC'd to 3.6 GHz with vcore set to 1.42 volts pulls 9.5 amps or 114 watts.)
I have seen 200 watts pulled off a 4 pin. So you can do a lot with a 4 pin if need be.
But I want to reiterate that the psu is of concern to me. There are lots of good PSU's with a 4 pin but most 4 pin psu are not so good. I am very interested to hear the OP's PSU model.