I have a Parasound 5 channel amp in my home theater system. There are only a few inches between the amp and the shelf above. I use one of these with front exhaust. It works great and is very quiet. They also have models with top and rear exhaust.
https://www.acinfinity.com/component-cooling/component-fan-systems/aircom-s10-receiver-and-av-component-cooling-blower-system-front-exhaust-17/
https://www.acinfinity.com/component-cooling/component-fan-systems/aircom-s10-receiver-and-av-component-cooling-blower-system-front-exhaust-17/