1.65v is Intels "maximum recommended" voltage. They also tell me i shouldnt be pushing 1.6v through my q6600, but i do that anyway
You just have to know the other voltages to keep an eye on. If i recall, you need to keep the RAM voltage within .1? of the QPI voltage, but dont quote me on that. As for the p6t, i'm using one right now while my evga board is out for repair, its not a bad board, but i still prefer my evga just for the sole reason of it being a LOT easier to deal with evga RMA than asus.