Before you get upset do this and you'll see where your choke is. First off ditch the VR and set your resolution at 720 or 1080p and look at your FPS. That tells you how fast your cpu is capable of processing and sending the data to the GPU because at the lower resolutions you won't be GPU limited. So if you 100fps then your CPU can handle the data needed to achieve 100FPS.
Now crank the resolution up to 4k and do the same thing (use fraps). Look at your fps then. At that resolution you'll be GPU limited. Anything lower than 100FPS means that no matter the CPU you won't really be able to get anything above that number because the GPU is already handling the info the CPU is handling at it as fast as it can.
VR is so demanding that the GPU is what's bottlenecking you. Upping the CPU just means you're going to be sending information faster to the GPU. If the GPU is already dealing with that info as fast as it can you won't see any increase.
The 1700 at your specs is a great processor and has plenty to handle what you're throwing at in VR. Your GPU is a huge bottleneck. Changing from the Ryzen system to the Intel system is going to cost you a new processor and mobo. Just sell your 1070 and up it to a 1080ti.
Plus the game is largely single core dependent. Again at the higher resolutions it's all about the GPU because the CPU is already sending the data faster than the GPU can crunch it. There's zero point to go with the 8700k or anything for this. I just built a system with the 7600k which at 4k test show it's like a 1fps difference. Now if you do something that needs HT and more cores, like editing, then go for it but for gaming you need to take all that cash and put it into the GPU not the CPU.