Time for a CPU upgrade! I can almost hit 10k with my 6850k (4.4GHz, barely stable) and 1080Ti (+200/+500 if I recall). NVIDIA GeForce GTX 1080 Ti video card benchmark result - Intel Core i7-6850K,ASUSTeK COMPUTER INC. RAMPAGE V EDITION 10
Yea, I can really notice it on TimeSpy. I couldn't crack 9k with just the one 1080ti. That was OC'd to +175/+400 and still not there, almost but not quite.
But going to wait for the CPU upgrade till I see how things play out. With coffee lake and such coming I think it is smart to wait.