I know this is an old thread but.....I found this on a search and it fits what I'm trying to do with my 06 X15. I currently have 2 amps, a mhd 600/4 that drives the 4 cabin speakers and a mhd 900/5 that drives the sub and two factory JL tower speakers. My first option was to add another set of factory cans with JL's but it's proving too difficult to find and buy a used set so.... I'm now considering replacing the single towers with Bullet hp 770's. My question is will the 900/5 drive the 770's sufficiently bridged or will I need to switch wiring and run the cabins from the 900/5 and the tower speakers from the 600/4?