Extra thermal compound is not necessary when you have a D15. Noctua includes stuff that's just as good if not better than most pastes you can buy. Silver 5 is inexplicably overrated.
OP - What kind of programs are you intending to run with this system? If you really want to run Ryzen on that kind of budget, you should at least wait for the R5s and see what kind of horsepower those bring. If you really need the extra cores the R7s are probably better for that, but again it would all depend on the types of programs being run.