So basically I have 3 choices. I can buy the same card I have now and put it into SLI. Or, I can buy a 780 or 780 ti. I truly don't know what I should do. I can get another 670 ftw for around $200 used on Ebay. A 780 is between $400-$500, and a 780 ti is $600-$700 give or take. Obviously, if I got a different card, I could sell my old one. Is Nvidia known for doing decent sales on special occasions? I'd like to get some opinions on this matter.