I had a leftover 10" MTX sub and a 140 watt Autotek "Street Machine" amp left from my previous vehicle. I took it to a local stereo installer and they did a great job with the installation. They used the same box, wrapped it in new carpet and gave me an extra long cable so I can move it where I want. Currently I have it placed in the left passenger footwell behind the driver's seat; this way I don't have to blast it to get the sound and feel I want. The installers mounted the amp in the spare tire well to the left of the battery and it's hidden very nicely. The last cool thing they did was to install a gain control on the dash, right between the rear wiper control and DC power port. This way I can remotely adjust the volume on the sub and custom tune it to the music I'm listening to. Total cost of the project was $300, which included labor and parts to connect my old equipment. The look is completely stealth and I haven't lost any room in the cargo area. I'll get some pictures posted this weekend. Oh, and the stock 8" sub is still connected.

 

Pics are uploaded...click on the camera icon under my username.

 

Pretty neat setup. I wanted to put my amp there as well. Just worried about airflow. Mine is currently on the box. Might as well make an easy package for the crook to run away with when he smashes the window. One of these days I will mount it better and secure the box in a more permanent manner. Until then I can look for ideas from you good fellows that post pics.
Blessings

 

Ventilation shouldnt be an issue down in the spare tire well. The battery is there and that requires good ventilation, which gm provided using a large vent right beside it under the corner of the bumper cover.

 

I was not aware of that. Thank you very much sir. I was thinking of getting a class d new style to generate less heat. My current is an old school orion hcca 250 running about 250 rms x 2. If it is vented down there though, the 15 year old amp will be alright. I was worried about long trips, that the stale air could warm and create a bad environment. Looks like the op's method is the way to go.

Thanks guys.

 

I dont know that amp specifically, but being a nice old school amp it will probably be too big to mount in there. There isnt much room.
Give it a test fit first. It might be easier to pull the plastic trim piece across the rear, gives much better access.