Need help with new build monster

I am building a new system which will consist from Asus Rampage x 79, I7 3960x, either Gforce 690 or 1 680 later followed by another 680, 2 *250gb SSD's Crucial or similar, Segate Baracuda 3tb, Crosair vengence 1600 4*4GB or 8*4 (need advice on that as don't think that I would be able to use 32gb fully, so it seems like wasted money), case NZXT 800 (or any other, I am open to suggestions), have not decided on the PSU as am not certain how much power will I need. And now for the hard part - how to keep it all cooled? Would it be possible to do it with fans or a cooling system would work better? Which parts to go for in terms of case, fans and CS? All suggestions will be appreciated. I already have 3960x and the Segate HDD. The Pc will be used for games, video and data editing. If my calculations are right, Gforce 690 consumes less power than 2*680's. If I will go for 690 I could instal another one later and have them both running on PCI 3.0 16*16, or because they have 2 GPU's each GPU will run on on 8?  
If I am not misstaken I will ned aproximately 1200-1300 PSU? Can anyone comment on this?