I, a big fan of building custom panels or racks in my trunk to mount my amps. Theres a milliong things you can do. And yes, I also mount my amps wiht foam underneath them to absorb some of the vibrations.
cool tips to mounting/keeping things clean:
1) build up he floor with mdf or wood so you can mount things to it
2) put strips like an inch and a half high under the bottom, run all your wires underneath in the free inch or so.
3) drill holes through the mounting board only where needed to bring the wire up from underneath
4) wrap this board/rack with carpeting or other fabrics
5) utilize fold down seats as places to mount, even building into the seat
6) ties down, ziptie,, or loom and exposed lengths of wire
7) mount the board/rack by bolting it to the car, or even just making it so it is jammed in by the box or something
8) mount soft foam behind amps
9) take foam /paneling and make cutouts for your amps, leave space for the heatsink to cool! then put these over your gear. It gives the appearance of a fluch mount plus hides every single wire
I could go on forever.. but you get the idea.. way too many people box mount and leave wires all over the **** place