Actually Bose doesn't recommend using two systems for stereo. They warn that phase cancellation can be a problem doing that. The PAS was designed to disperse the sounds BETTER than stereo. You can visit their site and get a complete explanation about this unique system.
Conventional thinking does not apply.
Personally I don't care one way or another if anyone else uses the PAS. I just know how it sounds and the amazing response I've had since using it.
DonM