Depending on amp specific you're dealing with there can be convection cooling interference that might lead to decreased cooling / higher working temperatures. Also consider that resonance / vibration issues are affected by say footers and placing the piece as mentioned might render a different sound presentation. Another $.02
Any harm in using an amp with the face down
For space and conection resions I'm using my center channel amp (NAD 2200) with the front facing the ground and the rear apron aimed at the sky. My question is, does any one know if this is harmfull to the amp or any resion why this shouldnt be done?? Thanks