Sennheiser pc 363d. All i say is OMG! Best headset i've ever used. Fits perfectly, GREAT sound, pretty good microphone.
https://www.amazon.com/Sennheiser-Performance-Surround-Gaming-Headset/dp/B008O515CK/ref=sr_1_1?ie=UTF8&qid=1474818900&sr=8-1&keywords=sennheiser+363d
Well, what are you going to use your PC for, if you are buying a 4k screen you wont be able to have 144hz which could be game changing depending on what games you play!
If i could choose between an 4k 60hz or a 1080 144hz with 1 ms respond time i would probably choose the 1080 144hz with 1...