I wouldn't think twice about using a different centre channel than what is used for the left and right channels in a home theatre application. However, it is critical that the centre be tonally matched. The centre speaker reproduces information that is in phase, i.e. mono. Usually this is voices that are in front of you on the screen. The centre speaker can be optimized for the reproduction of midrange, which is the frequencies where the voices are located. When voices are off-centre, the information is out of phase and in stereo. The left and right speakers will take of care of it, but they must be tonally matched so it doesn't sound different from voices reproduced in the front. Using identical speakers all the way across obviates the tonality problem. And that's fine, but it fails to take advantage of the speaker specialization that the centre is designed for and which enhances the home theatre experience.
Music and home theatre are not the same. You can't automatically apply what you would do in a two channel stereo to a multichannel home theatre. A single centre speaker is not a stereo speaker, Neither is a single sub. A sub is another example of a specialized speaker that exists in home theatre that many two channel people have no use for. Same logic and principle as for a centre. You give something up, i.e. integration, in order to get something else, i.e. low frequency reproduction of effects at louder volumes. It's not needed for most music, but it enhances the home theatre experience.
On the other hand, for discrete, multichannel music (or older, alternative forms of stereo using three speakers), I would want all speakers to be identical, front, centre and rear.
Music and home theatre are not the same. You can't automatically apply what you would do in a two channel stereo to a multichannel home theatre. A single centre speaker is not a stereo speaker, Neither is a single sub. A sub is another example of a specialized speaker that exists in home theatre that many two channel people have no use for. Same logic and principle as for a centre. You give something up, i.e. integration, in order to get something else, i.e. low frequency reproduction of effects at louder volumes. It's not needed for most music, but it enhances the home theatre experience.
On the other hand, for discrete, multichannel music (or older, alternative forms of stereo using three speakers), I would want all speakers to be identical, front, centre and rear.