I've seen a few posts on here where amps are mounted in seat backs. All the pics are of a double rear seatback. is this possible in the cars with the two single rear seat backs or 50/50 rear splits?

 

as long as the amp is smaller but think about cooling it looks cool but it will take life away from the amp if not vented and and kept cool and if you run an amp in 2ohms id really think twice but what you want is a box a lil bit biger than the amp with some fans

 

You should be able to do it if your amp(s) are small enough. May want to go with something the runs on the cooler side if you're not going to be using fans (a class d of sorts). When I did my setup (single rear seat mind you) I just made a frame for the amp to be bolted to and put in some padding/stuffing so that the seats were still semi-usable. You will have to get a bit more creative with wiring, but if you're attempting something like this, it shouldn't be that hard.