Budget restrictions is the other concern so in that case there is nothing wrong with going with the 990x especially with that HIGH a price difference. Use the difference towards a better PSU since all your components are going to be relying on it for good and stable power. Recommended for 2 x 660Ti is 620watts http://www.realhardtechx.com/index_archivos/Page362.htm so a quality 650watt will easily handle it.
here is the motherboards. Im looking for the most stable+cheapest sli i could possibly built with a nice overclock no need to get 5ghz or something because i saw from benchmarks doesnt give +4fps from 4.4 to more. so... motherboard+memory combo is my real problem here.
Maybe i need more than 1600mhz corsair 4x2 ram (on hz) to be more stable at oc?
If you overclock on the FSB then I would go with 1866 for more headroom but remember the memory controller is on the CPU and less speed and faster timings does not affect the controller as much as high speed and loose timings which can limit the actual CPU clock potential.
nice, so no big deal here, looks like im gonna bet on 8320/xa/2sliti/thermaltake 730w combo.
One more question mate. I dont have more money to buy another cpu cooler but im planning to buy 212 evo afters. Will the stock handle 4,2 , 4,4 ghz on gaming? im not going for more. how much temps i play?