Excellent answers above.
To oversimplify, there are two (somewhat opposing) philosophies that people will hit you with.
1. If you prefer something then there is no reason not to use it. If we are not happy, then what's the point.
2. Axiom speakers are designed to re-create sound as close to "exactly as it was recorded" as they can. Using the artificial sound modes like "Concert Hall, Jazz Club, etc." does introduce artificial 'extras' and the purists tend not to use them. Your choice of stereo or PLII to get surround sound extracted from a stereo source like a CD is entirely up to you. Use what you like and don't feel guilty for either as your still listening to the real thing.
