See my post #566 in this thread (back 1 page). Tight cabinet, barely 2 inches on each side. I didn't want to disturb anything either, but I don't like a fried or acting-up recv. from high temps. I used the 4" fans inside of a laptop cooler (they are like 1/2" thick if that), and glued them to a coat-hanger with bathtub caulk, masking taped it to the top of my 622, and they blow into the exhaust vent. My temps are VERY cool, and this is cheap, and doesn't affect warranty at all. Pic in my posting...
It looks like there's more room in my cabinet, but that's an illusion caused by my pulling out the receiver a bit to get a pic of the fans.