Ditch the liquid cooling.Air cooler is fine. A $30 cm hyper212 will be all you need. Quieter, and more reliable too.
triple stick kits are ok, but usually used on X58 based motherboards.
In a Z77 based motherboard, one of the sticks will only operate in single channel mode.
In this case, if you need 12gb, it will be better and cheaper to buy a 16gb kit of 2 x 8gb. for $50.http://www.newegg.com/Product/Product.aspx?Item=N82E16820231489
XFX is a good brand, and 550w will run the 7970:http://www.realhardtechx.com/index_archivos/Page362.htm
Look at the Antec earthwatts green 650W unit. $39 after rebate:http://www.newegg.com/Product/Product.aspx?Item=N82E16817371044
What will you store on a 1tb hard drive?
A 120gb ssd will hold the os and a handful of games. Perhaps a 180gb or 240gb ssd would let you omit a hard drive altogether. You could always add one later.
Most any Z77 based motherboard will do. You should be able to find one <$100.