While I can vouch for the R7 1700 being an extreme amount faster than the i5 750 as I also had this upgrade path, the 750 is not exactly the kind of CPU we’re talking about here =p
Stock 1800X should be faster than stock 6800K.
Honestly I find it hard to recommend one over the other, if you do OC, the 6800K is probably the better buy but at the same time the 1700 is a much better buy than the 1800X, again, IF overclocked.
If you don’t want to OC, and just want something fast for building lightmass & shader compilation, and don’t want to pay for the 8+ core Intel CPUs, buy the 1800X.
In that benchmarking thread I’m only running the 1700 at ~3.5Ghz for most of the tests, while all other CPUs were OC’d to over 4Ghz.
I didn’t know this before, but apparently visual studios linker is single threaded, which explains my CPUs surprisingly poor code compilation results, by overclocking to 3.5Ghz, I actually lost 200Mhz of single core speed, so a higher clocked Ryzen will be pretty competitive there as well.
It’s all too hard, sorry for not really helping =p