Marklamarkleis most likely right, for most games a 2.5ghz i7 is fast enough to more than balance a 970. To see if this is true for YOU, look at benchmarks of your favorite games and see if they are video limited with a 970 or CPU limited.
Aside: Was this 2.5Ghz part the Intel Core i7 2860QM ? If so that's a 3.6 GHz beast on turbo, and absolutely will not be the limiting factor for any modern game. Or was this a different CPU ?
Aside: bottleneck is something that always happens. Something is always the limiting factor on framerates. It's going to be video or CPU or memory or ....