Ok, so 8120 at unknown clocks, no clue on the motherboard, 12GBs of unknown configuation or speed, sitting in a case of unknown size, displayed on a monitor(s) of unknown resolution and powered by god only knows what. Thank you for filling in the gaps.
General advice I can give. Assuming a single 1080 screen I wouldn't bother with a 690 or 790. You have no use for a dual card. A single GTX680 or 7970 should be enough for what you want.
sorry i cant reember everthing i put in it made it a while back im also gaming a 1920x1080 but i will be upgrading to a montor that is 2560x1440 and i was think the 690 as i want to be able to play games on max in 2013 and the gtx 680 will drop a bit short then