Do you happen to have the setup already? or is this a proposed build?
Every system has a bottlneck.
You may suffer CPU bottlneck in one game and not in another.
Theres many variables to work through to give you an exact and correct answer.
Depends on the game, depends on the fps your hoping to acheive.
If you played an MMO that only runs on 1 or 2 cores and you were trying to shoot for 120fps then i could see the possability of a bottlneck in terms of not being able to...