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 is unavoidable? 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 only on 8?
If I am not misstaken I will ned aproximately 1200-1300 PSU? Can anyone comment on this?
need advice on that as don't think that I would be able to use 32gb fully
RAM: Worried about the added cost of ram when your already spending $1000 on a cpu? Imo if your going for a Monster build might as well go all out also if you go the 32gb root then you have enough ram to partition some of it as a ram disk (That's not first hand info, just what I've read on different posts so I could be wrong, do a little googling and I'm sure you will find the benefits)
GPU: I'm fairly confident PCI-e 3.0 x16 bandwidth isn't needed for current gen cards purely because last year cards weren't maxing the bandwidth in a PCI-e 2.0 x16 slot, I wouldn't let the bandwidth numbers get in your way when making a GPU choice. The way a 690 links it's GPU's is a chip that runs x16 bandwidth to each GPU and then x16 out to the PCI-e slot, the chip they used on the 590 (Which works essentially the same way as the one on the 690) was also used on some motherboards to achieve x16 bandwidth on 2 slots as opposed to x8x8 bandwidth. Also consider 2x680's will perform better then a single 690 because the clocks on the 690 are lower but the GPU's are identical.
PSU: With your PSU, a lot of people seem to go bigger then they need to, really you just need to calculate max TDP of all your parts together +10% for peace of mind. If your running 2x680's with a i7-3960x you've got 195w X2 + 130w + system usage, which is all of 530w+ (Though that probably wouldn't cut the mustard) and even less running a single 690. I'd be more inclined to go with something like a corsair ax-850 for a build like that though as stated before if your going monster you can just go all out with a 1200w monster and then have room for quad sli or similar. You can use a PSU calculator to get a baseline for what you need http://extreme.outervision.com/PSUEngine I ran a quick build just then with 3960x + 680 sli with a couple HDDs and fans etc and it recommended 600w PSU. I'd be looking for an 80+ Gold or better Modular PSU for a monster build though. Also remember if your overclocking to check what effect that has to the TDP, as you increase the voltages the TDP is going to zoom up and the more parts your going to overclock the more headroom on the PSU you will need. There's a lot of good stuff to look for with a good PSU like Japanese capacitors, 1 vs multiple 12v rails (I've read sites claiming both are better) but the easiest way is once you know how much power you need, and then go by 80+ certifications and whether or not you want a modular PSU (you should they are awesome)
Cooling: Your looking down the barrel of some choice hardware, So it'd be foolish not to suggest you sink that rig under water. But if you don't wanna go down that route can always chuck some big air on their like a Noctua NH-D14 or a Promlimatech SuperMega. As long as all your case fan mounts have fans in them and a decent Heatsink on your CPU you should be good to go. If your not sure about orientation front/side fans as usually intakes and rear/top fans normally exhaust.