For the long haul, very likely that the extra threads are more important than a bit more single threaded performance for anyone.
The main focus is the i7 8700>8600K because at that point do you really need another 10-15fps with the 5ghz 8600K? You can also get away with less cooling for the 8700(non K), and it doesn't really need to be delidded since you aren't OCing it
Otherwise if the best 144hz is the goal that budget can easily fit an 8700K.
i7 8700 or R7 1700 > 8600K always IMO
Just seems to better to me to have more threads rather than some extra single thread performance when the i7 8700 at least already boosts to 4.3ghz
Also seems weak on performance per dollar
Pretty much no reason not to go X99 for a build with that budget, at the very least an i7 6700K