To be honest, your cpu probably isn't really your bottleneck in VR. It' s Haswell 3.4GHz, up to 3.9Ghz; no slouch, even when left at stock speeds.
It probably is the technical bottleneck, but with a 1080GTX and a 3.5GHz or faster cpu, you've got the best VR experience right there.
Anything faster will only be incremental; you might spend money and not even notice a difference.
You could upgrade cpu, motherboard and RAM to future-proof your PC, but its a fair whack of money to spend for arguably little payback in frame rate.
Easiest way to check imo;
- Go back to 2D monitor as main output,
- Turn off V-Sync so you see the real fps output of the 3D card
- Load into the take-off/landing traning, so you end up in a Coriolis station for reasonable and repeatable load (you can't easily replicate a busy RES)
- Ctrl-F to flip up the frame rate. Note frame rate at normal cpu speed.
- Overclock the cpu using Bios tool etc, just mildly (+5% or so; I am simplifying this step a lot since there are many different tools and motherboards etc)
- Repeat Coriolis station environment test, note frame rate. It should be the same, or faster (not slower)
- If the cpu was limiting your framerate at the lower clock speed, then you'll see an increase now you're mildly overclocked (your graphics card is waiting for new geometry data from the cpu for each frame).
- If the frame rate stays the same, your 1080 is the limiting factor (unlikely, even at high settings so long as in-game SS is at 1.0 and not using the debug tool).
- Consequently, any time you increase a detail setting and the frame rate drops, you know the 1080GTX is the limiting factor.