EggXpert

Here's my planned build:  http://secure.newegg.com/WishList/PublicWishDetail.aspx?WishListNumber=14887049

For the video card, I'll most likely roll with the GTX 660 or 660ti once they come out; I've added the 670 just as a placeholder or unless I get impatient. :)

Anyway, I want to make sure I'm picking a PSU with appropriate wattage. Got a 750W supply in now, but from my calculations, 650W might be a little more efficient. Since this is my first time, though, I'm not sure if I'm right (is 650W enough power?) and just wanted to gather some other opinions before I pull the trigger.

Very nicely done. You must have studied a lot if this your first build.

Regarding the power supply, even with the GTX 670, you can go as low as the Antec Earthwatts Green 500W; that'd cover the overclocking the processor as well.  If you want even more extra, there are the XFX 550W and Seasonic 620W.  I don't know how much power the GTX 660 / 660Ti is going to use, but it won't be more than what the GTX 670 uses. 

The only reason to consider more wattage would be if you are interested in SLIing the grpahics card.  With 2 x GTX 670s in SLI, the 650W version of the Corsair Enthusiast or Professional Series might be okay, but, it's better to get the 750W version. However, since you are getting a lower tier card than the GTX 670 here, the 660 / 660Ti, 650W would be enough for SLIing the card that you are getting.

Anyway, if you are interested in SLIing down the line and you can easily afford the 750W, the 750W isn't rediculously overkill.