Best upgrade from my hd 7950?

[RacA]

As far as I do understand i5 3570k will not bottleneck gtx 1070 in 1440p in most cases.

This is best approximate explanation I can come up with:

If you would have wanted to play on 1080p 144hz display then yes, your cpu would be a bottleneck as gtx 1070 can generate 144 frames in this resolution and your i5 can only process data for 60 frames. That means you will not see any improvement over gtx 1060 which can generate 60 frames. (You will end up with 60 frames anyways not using full potential of your screen).

If you play on 1440p 60hz then your gpu will have to do much more work and will generate only 60 frames and that is what your cpu possibly can keep up with. You are using 100% of your gpu power and 100% of your cpu power therefore there is no bottleneck.

 

Of course that is very approximate example which does not reflect all the scenarios but if you are playing gta v, witcher 3 or any other AAA titles on 1440p, you should go for 1070 not worrying about any bottlenecking.