I’m running 2 x 1080 with a 6900k.
1080’s only help while creating depth maps.
so if thats taking a while it will speed that up.
it depends your scenes on how much it will help vs a faster cpu.
but if you have lots of photos/high res. gpu’s will help.
if you have large area’s and want high detailed meshes, they get more cpu intensive.
for the project i have been doing, I find the cpu the bottle neck. normally around 20% gpu time 80% cpu with this setup.
in and old setup with 1 x 770 with 3930k. I found it around 50% gpu 50% cpu.
I haven’t tested rc on my 6700k (if it was floating license i could test it). but i suspect it would be pretty good. I do find parts of the processing can drop down to single core in parts. and 6700k would do quite well there to make up for less cores.
I do also notice 1080’s, running at around 30% a lot of the time. (they normally start out at 90%-100%)