jsc :
I thought the Intel recommendations for "do not exceed voltage" for the first generation Core 2's was 1.5 volts.
Correct, IIRC. They will run fine at that voltage, unlike the 45nm parts which have a max voltage of 1.3675 according to Intel. Also, you can slightly exceed those recommendations and still be fine. I'd feel comfortable up to about 1.4V on a 45nm part, and 1.55V on a 65nm part. Of course, this assumes good temps.