Lol didn't even notice he had 16GB, yeah save on the RAM, 8GB is plenty for even the heaviest of users. The i5 2500K vs i7 2600/700K is ultimately up to the user, if the user is heavy multithread like video editing or computing then go i7. But if your are ONLY gaming the i5 2500K is plenty.
Well I'm not exactly sure at the moment. 7870 hasn't been released yet but check reviews for different models. All companies are generally good. Get non-reference model card as they're much cooler (generally) and better (generally)