I used to have the lifestyle 12....several years ago. its really the same as the newer system, double cubes, bass module, cd player with am/fm radio, it was a 5.1 system. after about a year (keep in mind, this was around '97), i decided that i needed more sound, louder, better. so, i went to best buy and bought a receiver. when i realized that the main connection from the sub to the unit was a proprietary plug, no chance of hooking up the sub. so, i figured, i'll buy a sub and keep the satellites. nope. the cubes sounded terrible. it was all midrange and just simply didn't get loud - at all. it sounded like a 80's transistor radio on max volume.
after talking to a few bose reps and reading everything i could find, i learned that the lifestyle systems are developed around the sub and cube - they need each other to function. the sub has the amplifier and x-over built into it to drive the cubes. the system also has some funky impedences which is why the sound was so quiet.
if i may comment on one of the above posts? the acoustimass systems are different than the lifestyle in that they CAN be hooked up to any receiver. that speaker set-up is passive and therefor needs a 5.1 or greater channel receiver.
if you need to hear this for yourself, do what buckeyfan said....or go buy a receiver that you can tinker around with that you know you can take back a few days later.
fyi....their oem car systems are the same way.....either leave it alone or tear it all out. there's no "in between"