I would keep your i7 2600 for gaming. Ryzen R5/7 had fairly similar gaming performance as sandybridge CPUs at launch though it has improved some since. The i7 2600 is still a strong CPU for gaming and has more threads then the r3 1200 which is becoming more important as of late in gaming. going with a Ryzen R3 CPu would actually be a downgrade in gaming. I am sitting on an i7 3930K 6C/12T @4.2ghz for the almost the same reason (which is same cpu architecture as yours, sandybridge plus 2 cores/ 4 threads). When Ryzen 2 launches that might be the best time to pull the trigger for your next build. I am forcing myself not to build for now for basically the same reason....though if the i7 7900X drops to $799 or less now threadripper is out...