970 still kicks ass in nearly all situations regardless of the 3.5g memory issue. and a cpu upgrade wont do that much as most games are not cpu limited. Plus to get a good cpu, you'll probably need a new mobo too. What kind of core2 do you have, 2500k or so? Unless you are much older than a 2500k I think you are better off spending on gfx. Also an SSD if you dont have one, those are the two best upgrades for most systems.
if I was you, I would wait until the price drops on a 970 and then sell your 760 for $100 bucks or whatever you can get. Then use that money to upgrade to a 970. or wait till the 960 TI comes out for a better midrange option than the current 960 (960 is not really an improvement over 760).
I do that trade up tactic all the time. I sold my 760 four months ago for like $130 I think... if you time it right and dont wait too long to sell, you can make back around 60-70% of what you paid. Then I used that to buy a 970. You can try amazon or ebay (or craigslist if you want to trade it for sex.)
