I think you would be fine with the GTX 760/770 for now but at some point you will want to upgrade the rest of your system as it is aging. Also note that the free ram offer is only for one stick of ram for best performance you would need two sticks for dual channel ram and you can get good quallity ram in a 2x 4gig kit for less than $72.
Getting a upgrade to the GPU now might be the best option and the save your money and do a system upgrade later. You can carry the new GPU over as well as the PSU hard drive and such at a latter date.
Even though it may not be utilized the best it could it should still be a good upgrade from the GTX 560ti you have now. The problem with upgrading the rest of the system now and keeping the 560 would be that it would hold you back and I am not sure you would really get much of a benefit from it until you upgraded the GPU.