I was put in a similar situation but with a GTX 570. So instead of increasing the heat and power consumption with a SLI setup, I upgraded to a single Gigabyte GTX 670 WIndforce OC X3. I love this card because its quiet, OCed, reliable, and benchmarked faster than the Galaxy 680 model stock. For $299 this might look small but it has a very cool design over a custom PCB. I recommend the newer generation card because if you do 560SLI then you might have to buy a 800W PSU. I use a OCZ Modular 600w for my 2600k, and GTX 670 Windforce X3.
Hmmm. Not too shaby, I would say not too much bettter due to fan design. I read about once the fan kick in they can get pretty loud but not as loud as the other one. For his/her price range I'd recommend this too but it all comes down to whoever posted this topic. That said maybe he/she doesn't care about the heat or sound level lets see what one he/she picks that best suits them.