A 750W Power supply will be more than adequate even if you overclock or throw in a mid range graphics card. I have built a few using the Corsair builder series and I am impressed by the build quality and price. Enermax also builds decent power supplies.
I agree on motherboard brand as well. Asus is always a good choice. Gigabyte and MSI are also reliable and feature packed.
Is there any reason you aren't considering a Z68 based motherboard ? It has SRT support where you can use a smaller SSD (max 64GB) as a cache for a larger spindle drive. It also has Virtu which if you add a graphics card down the road it will let you use it and the onboard Intel graphics
Overall should be a nice system. There are plenty of build guides around if you want to brush up before the build. Maximum PC has a few guides that I know of.
Food for thought anyhow, have fun with the build.