I remember speaking to someone via Instagram who replaced the fan in their ABM for a high spec PC one, with the same size and voltage requirements.
It was whisper quiet by comparison, and when I say high spec, it was still only about £20.
I might do it in the future, but to be fair to Ashdown, how many people who buy a 600W ABM are that interested in playing along with an acoustic set up? These amps are for loud stage use, they make plenty of smaller, and probably quieter amps and combos for when a lighter touch is required, no?
Eude