I was going to get a gtx 460 1 GB at least and pack the thing with hard drives, and a couple DVD drives. So I was planning on the 700 because according to the extreme psu calculator with one hard drive and one DVD drive I would need at least a 540 watt. So since I planned on putting more stuff like DVD drives, hard drives, fans, and mods I figured that it would be safer to go with the bigger power supply for the same price.
Don't get a 460 - it's 3 generations old now. If you're going to get a video card in that price range it'd be better to go with a Radeon 6850 or even a 7770.
That will be a good setup - the 2120 is a solid CPU for the price.