Arthur, welcome. After seven years now with my M22s I'm still delighted with the superb sound quality that they deliver when the source material is of high quality. As to compression, all speakers are subject to compression at some point, where adding more power simply heats up the voice coils in the drivers more, but the sound level doesn't increase. Even the M80s are subject to this, as Ian has mentioned in his description of power testing of the M80s that compression developed around 118dB. The M22s don't have that high a sound level capability but for sane listening levels in anything but a huge room at a long listening distance they do the job.
For most music they can do a adequate job in the bass without a sub, but for some music(e.g. pipe organ)and for LFE(low frequency effects)occasionally present in movies a sub is highly desirable. I use the EP500, but a suitable choice for you would depend on your budget.
