Have the XPA-5 Gen 2 amp and have been using it for 3 years; it is excellent. You can switch from 5 to 2 channels with a pre (use the XMC-1 myself) and it makes going from movies to music effortless.
If you mainly/only listen to music I would recommend you stick with a stereo setup; the XPA-5 is not necessary for this. Most music is mixed for stereo and you get a better soundstage with two speakers and channels. Even a subwoofer will interfere with low bass imaging (2 are much better).