i wouldnt worry too much about it. try it out this winter, put the heat on just legs full blast, and turn your music up and drive for a while. the amp will go into thermal protection mode and will stop working until you either turn off power, then turn it back on, or the amp cools enough to turn back on on its own. MAKE SURE YOU DO HAVE THERMAL OVERLOAD PROTECTION BEFORE YOU TRY THIS THOUGH. IF YOU DONT, YOUR AMP WILL FRY. if it does get too hot, install a fan down there to flow air over it, a little fan from a computer works well.

 

Unless you make the car hotter than the amp (which i don't you would) then you shouldn't have a problem. But also, when an amp is to cold it will run less power and heating it up will probably help to get it to normal running temp. I would consider blocking the vent if you were going on long trips tho...

 

I had 2 alpine amps under both seats for over a year, in NJ and never had any problems.. My girl likes the heat (something genetic with that?? all women like it hot...) anyways she'd keep the heat going full tilt.. the alpines have cooling fans built in wich couldnt hurt, but I never blocked the vents.. but if you never have people in your rear seat it really wouldnt hurt.. plus youd get more pressure on your front feet.. hmmm maybe I'll do that now that i moved the amps..