If you already have a Q2 and you are defo going to get the new GPU, why don't you wait and see what you can get out of the Q2 before you buy another HMD? I went from a 1070 to my current card and love my Q2. Have you played with the bitrate settings? I find it grainy as heck with default. I have it set to 900 and it looks great IMO.
That said, you can't go wrong with a second hand Reverb G2, though it might be worth checking which version it is as V1 had some issues which were completely fixed with V2. I don't know how you would tell this though.
The Pico Nea 3 looks interesting, as I think it uses DP, so theoretically uncompressed. BUT both Reverb G2 and Pico Nea 3 relies on Steam VR runtime which performs noticibly worse than the Oculus runtime