I'd advise against it. I once worked on 4 SAZ-4500D's installed without the bottom covers, from a well known install that all had something get inside the amps in the car that was conductive and rattled around inside, when it landed across the high voltage (300-400VDC) in the output section it popped the amps.
Also it allows more dust to get in there, if you live somewhere that is a humid climate, once you get the dust in there, then the dust soaks up moisture on a rainy day or foggy morning, next thing you know, you've got a lot of conductive stuff all over your amps circuit board and eventually it will arc in the high voltage and mess it up. Also the various things that make up the "dust" once mixed with water, become corrosive, and slowly corrode any exposed metal or copper on the circuit board/in the amp. Bad Idea. Cover is good, leave it. That's my suggestion.