I run a quad of toms modulus 86p boards as a pair of bridged monks. They're utterly silent in use not even a whisper from the speakers at way higher volume than I typically would listen at. Toms boards are super easy to build, though they'll stretch your budget for a pair of his 286's. I tried them against the hypex nc400 and the hypex had slightly better bass slam but lost out in the treble in my systems. Honestly both of them are stellar amps, best in class designs for sure.
Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m