Reliability and budget, hmmm, thats what we all seek. The KB45 motors are big, heavy, strong and powerful, but amp hungry, get hot etc. They have no cooling holes and would require a water jacket. I run a KB45 - 1700kv version on 6s in a 32 inch tunnel with the same esc you plan to use. Octura X645, cut back to 43.28mm, goes well. Even though manf says 36v, I reckon that's pushing it, BUT, they do it.
I think you get what you pay for and things can definately be done on a budget if you look after them and know the limitations. Mans got to know his limitations, lol.

PS - Welcome

Peter