The most info I've seen on the bose setup.
The amplifier also serves as a crossover. All speakers connect directly to the amplifier. If you're considering replacing just the amp or just the speakers don't do it. You will either need to power the speakers off a new headunit's internal amp, an aftermarket amp or wire them differently to the stock unit which also has an internal amp- you might have to code the unit differently in order to make it output on those channels. Wak has a DIY on that too listed as mega bass.