I was thinking about getting a setup that utilizes multiple sub woofer sizes. Whether it be a 15 and two 8s or even a 12 and two 6s (whether they be referred to as sub woofers or just woofer speakers at that point). Was anyone seen a setup like this? I'd like to see some images of the box set up and also have some questions. Can a standard after market radio run two amps? Is having two amps necessary? (as in one for the 2 smaller subs and one for the large one)
Run any number of subs you want but all identical, you can run many amps, usually you setup one amp for bass and one for all the higher frequencies, if you want to run 2 bass amps you can use Y splitters, you run two bass amps or more until you reach the power of all your subs, when multiple amps are used usually a line driver is used prevent the HU from overloading.
Now a couple extra drivers being used for mid bass or even rear fill usually works well depending on your goals and set up. I also would not recommend two different sized subs, especially not in the same box.