I just picked up the AC Infinity S10 version (front exhaust)
from Amazon to cool a Denon AVR-X4400. This amp runs a lot hotter than the Denon AVR-2310C that it replaced. After 10 minutes or so of use the top cover of the X4400 became hot to touch, indicating much higher temps internally.
The AC Infinity S10 unit is a front exhaust version with 3 fans, claiming 160 cfm at 24 dba. I measured 46db (A weighted), about six feet away from the rack with the fans manually set to full speed. You would definitely notice that.
The good news is that with AVR-X4400 at near reference volumes watching a full ATMOS sound track film (11 channels active), the S10 unit fans did not reach 50% (based on the LED indicator on front panel) and the fan noise was not noticeable in the 10ft x 18ft room. The receiver chassis remained cool to touch, and exhaust air was warm, so it was obvious this unit was doing its job. The fan unit pretty much covers the entire top of the amp, is very low profile (about 1.75"), and is definitely built to take the 30lb top load they indicate in their literature. The S10 has several modes, but I found that "Smart" mode worked well as the fans stayed off when the amp was first turned on, and then gradually ramped fan speed as the amp warmed up.
"SMART MODE - Both the orange and white light will be visible to
indicate if the system is running in SMART Mode. In this mode the fans
will change speed depending on the measured temperature. For every
2° F increment that the temperature is below 88° F, the speed of the
fans will decrease by one level."
The S10 is a quality addition to the equipment rack. I paid full price, and have nothing to do with the company. I do like to speak up though when I find a well built, cost effective product that works as advertised.