Would 2 GTX 660 perform just as well or better than a GTX 690, is it worth the money? or should I stick with one graphics card, would a 750w power supply suffice for 2 oh these?
No, 2 660s will not outperform a 690(2 gtx 680's). A good 750w psu willl power 2 660's, while a crappy one will probably just pop and fry the system. Is it worth it? Well that depends on what games, resolution and settings you want to run.
I use a Cooler Master GX - 750W 80 PLUS Bronze Power Supply (RS750-ACAAD3-US) <-- will this be able to power 2 GTX 660?, also even though Im disappointed my graphics card won't be as good as a 690 its still worth it to get another 660 in a couple months and be equal to a 680.
The Cm gx 750 isnt a very well reviewed model. Quote from the hardwaresecrets review "High noise levels overload and can even damage components on your computer" this was on a 600w load I would suggest replacing it with a better power supply if you want to run dual 660's. http://www.hardwaresecrets.com/article/Cooler-Master-GX-750-W-Power-Supply-Review/917/10