i have an ASUS 1080p 180hz monitor. when i stream warzone i only get about 60-80 fps and non streaming is about 80-90. im just trying to get a higher and more consistent FPS rate out of some higher end games
Assuming you have the settings maxed out then that's about what I'd expect from a GTX 1070 (I'm running one currently). Are you encoding video on the GPU when you stream or the CPU? Based on the framerate hit you're taking I'm guessing GPU? If so, try swapping over to your CPU and see if that helps. The i9-990KF should not have any trouble encoding for a stream while gaming.
If you do still decide to upgrade your GPU, what's your budget? I'd say the best bet is to hold off for either an RTX 3000 series GPU or an AMD Big Navi GPU since we're seeing an impressive generational bump in performance with those. Otherwise a used or clearance GPU might be a good pick, depending entirely on price.
At 1080p, the horsepower of a GPU like the RTX 3080 will be mostly wasted. I'd stick with something more budget friendly like the upcoming RTX 3060 (or AMD equivalent) if you want to keep your current monitor.