upgrading to new Gen for me is always better and more future proof than just getting the same old gen and SLI . Some games does not support SLI and you will need a good PSU to handle two GPU . Also the scaling of performance isn't that greet ether . Unless you are getting the GTX 770 for a really cheap price and you have the capability of SLI then go for it . Otherwise I recommend getting the GTX 970 or maybe the AMD equivalent R9 390 .