Big Brother owns stock in ACInfinity. We had one on a Denon AVR-X3600H, because the cabinet was somewhat tight, and there were occasional shutdowns. No fan noise issue unless the volume went up and the Denon getting warm, then maybe some noise underneath the very loud music. At this location I have an old Denon AVR-2312Ci without the fan; cranking for a while will result in shutdown. Even moderate volume the unit gets pretty warm though not hot to the touch.
Is a fan
necessary? Eh, perhaps not. OTOH I cannot imagine it does any
harm so it's like insurance. Do ya feel lucky, punk? Well do ya?
The dust...the fan on top kept off the dust as opposed to the one here which gathers tons of dust (though full disclosure, the location is different). Mmmm, even if the fan does suck in dust I would not think it to be huge, and the constant airflow reducing the dust sticking, as opposed to if the dust settles out of the air.