Well I’ve not noticed the fan at all, but then we rehearse at same volume as we gig, not daft loud but we’re a punk band so unlikely to hear a fan with all that going on.
I’ve got the RM500 EVO2 as well. For regular stages and pubs not much between the two, but get on a big stage and the depth and feeling of sound from the ABM comes into its own.
Have to say though, the RM500 is the weightiest sounding small Class D amp I’ve had, and I’ve had Markbass, Aguilar, GK, TC amps, the RM for me beats them all - but the ABM does trump it.