I used to, until I took the amps out one day, and they were severely dented, scratched, and lost a lot of paint from the seat sliding forward and back.

Never again.

 

I guess it all depends
kelticslob's seat scratached and dented his, while I have mine under my seat and I have minimum 2" clearance all around. The seat never touches it, all the way up or back (and there are no broken springs or anything like that hanging off the bottom of my seat to damage it.

As for Chadxton, Heat shouldn't be an issue. They are inside the cabin of the car. In this light, when I feel hot, I cool down by opening the windows to circulate the air, or turn on the A/C to cool down. In contrast, in the middle of the summer the trunk can be stinking hot with no way to cool down.

It also helps that I have an air vent under the seat which passes air to the rear passengers and also keeps the air circulating around the amp to keep it cooler.

I have my seat far enough back that the rear passenger's feet shouldn't reach the amp (although one time my rear passenger's foot inadvertently turned my gain all the way down - that took me a while to figure out where my bass wnet).

 

uhmmm why would you have a system just to not play it loud and keep it turned down all the time :S
honestly, if someone wants something out of your car bad enough, they'll take it, and some take it with a surprisingly amount of professionalism.
ya placing them under the seats over even making little cubbies in the trunk for them with covers will help combat thieves, and always just park somewhere bright and open if you possibly can, alarms help for the thieves that may just be say walking by, or only scoping you out for a little while, but i've found that most people that go for car stereo's they follow you around for a while and get to know your routine better than you do... you just gotta have faith, drive safe, park in bright visible areas, and crank that alarm up to like 130db lol, nothing like a friggen fog horn to scare the crap out of an unsuspecting thief if they hit the wrong switch, and if the neighbours complain, tell them to pay for your stuff if it gets stolen then you'll turn it down...