It is hard to say exactly. The result will depend heavily on load and tasks that you plan to use. It will be much easier after conducting a tests, but for today we don't have such opportunity.How much maximum watts you manage to hit staying in a quiet and cool config ? 100w ? 120 w ?
I recommend to search for builds with Noctua NH-L9 and see how it performs on different CPU(not just Noctua table).
With case fans CPU temperature will be more stable and predictable during different loads, thus allowing a slight curve to be specified for CPU fan.