Transparent, musical, and detailed without ever becoming aggressive.

None.

Had to convert my 2 channel audio rig to multi channel. I was weary about finding a center channel that would match my NHT 2.5i, but the M5 fits perfectly. The voicing is nearly identical, except it seems to resolve even MORE detail than my main speakers, without ever sounding spitty or forceful. Very invisible, meaning the speaker never gives itself away. For movies, this makes DVD's like Star Wars even more involving. For DVD Audio and SACD, it is unbelievable. Yes' "Fragile" is a whole new experience in surround, even Bjork's "Vespertine" is delightful, as this center can handle her voice just as handily as it can dig deep into the mix to reveal Chris Squire's amazing bass playing. Every voice and instrument sounds amazing out of this center. Comes with a kickstand that allows it to sit firmly on oddly shaped TV tops, like my own. This speaker is so good, I'm very tempted to replace my 2.5i with the T5 fronts, just to get the full experience this system has to offer.