Basically, if I have any game open, everything else on my system slows down. My mouse cursor gets choppy, I have to wait a bit before a window opens/minimizes, and I can barely watch videos on YouTube if at all. Everything just lags. The game itself is fine. Recently, I've acquired the budget to get a new GPU and I plan to get the 6GB GTX 1060, but I'm wondering if that's what I should be putting my budget towards. I thought it was definitely my GPU, because it's absolutely pathetic but then my friend brought up the possibility that I might have slow drives. How can I determine what's causing me such horrific system lag? I know that it's not my CPU because it never goes above 60% load.
Most played game is Overwatch
Specs:
3x 1080p Displays, gaming on only 1
GTX 660 2GB
i7 2600k @4.2GHz
32GB DDR3