for 144Hz gaming with powerful card, you would be better with i7.
8 threads do make a difference in some games. otherwise you will have hard time to cross 100-120FPS in those CPU intensive games even with i5@4.5GHz.
If you can't fit i7 (with close to 4GHz frequency) into the budget, I'd recommend going for GTX 1070 and i7.
CPU lifespan is much longer than GPUs. Usually GPU replaced 2-3times on the same i7.