Parasound amps are outstanding. I had and A51 and A21 for a time, but in the summer they put off way too much heat in my room (Northern California gets quite hot). I ended up switching to ATI's digital amps (NCore) and they do an amazing job as well, but don't put off nearly as much heat. In fact, they rarely get to 100 degrees where the A51 and A21 would go north of 120 degrees.
I have an AC Infinity Aircom T8 cooling fan on my A51+ amp, and so far I have never seen it over 88 degrees, even after watching a movie like " Ready Player One " cranked to reference + 3 for 2 hours. I'll re - test it over the summer, although obviously we always have the AC on during the heat. It's the same temp as the Denon X8500 is ( which also has an AC Infinity T8 cooling fan ). Maybe these newer amps run cooler. Or, maybe my rack is better ventilated. Or, maybe I have way more power for my speakers now than I really need. I'll check the temperature tonight after watching " Black Hawk Down " in 4K at reference +3 ! That soundtrack is an ass kicker !
Craig, my amps were in an enclosed custom built rack that went into a wall space. I did add fans, which helped keep the amps cooler, but they warmed up the room by blowing the hot air out