You really should have no problems with that setup. I run the game at 4k and i have a geforce 970. i have a 3570k and 16gb ram. framerates are within the 30-60 range consistently.
Mainly because of the monitor, if I go with gtx 1080 and 1440p gaming I would like a gsync 144hz 27inch (minimum 650€) and with a 1080ti I would buy a 4k 60hz (400€) to play in 4K and CS not being a FPS game I think it makes more sense to go 4k 60Hz bearing in mind that there is virtually no difference in the final price of the build.Well you decided for the best and most expensive gaming components available then. Anything not working to your liking is to blame on the game, not the hardware^^