I want to upgrade my GPU but I don't want to bottleneck whatever GPU i end up buying, i am probably going for a 970 or a 980, but will my CPU bottleneck the performance?
Definitely, especially if it's paired with a good motherboard, cooling & is overclocked.
At the time I was looking at the i7-9XX CPU's but ended up going with the AMD Phenom X4 965 due to my budget and it's still going strong with a R9 290 at my friends house. Ended up overclocking the CPU to 3.8ghz and still games pretty good on newer titles (around 50-60 FPS).