If you are serious about SLI'ing that GTX 670, I would get a 750W PSU. It gives you enough headroom that your PSU will not be lacking juice. I have the xfx core edition 750W and it works great. Other reputable and reliable brands include Corsair, OCZ, Seasonic, etc..
Agreed, if you want to eventually double the 670 power go with a 750 watt. Other than that, yeah you've got a pretty decent build although why not spend a little more for a higher capacity secondary drive?