We hear with two ears, not three, and if a two channel setup is of sufficiently high quality and properly balanced in a room with no serious acoustic issues, and of course fed a well recorded piece of two channel music, it can sound as good as a three channel, which with two channel recordings is artificially creating the center channel. I don't know of anything currently being recorded in three channels, only 2.0, 5.1, and maybe a few 7.1 or higher, so listening to two channel in three or more channels uses a matrix system such as DPLII, Logic 7, or Circle Surround, to artificially create the extra channels. That can be a good listening experience, especially with Logic 7 music, but it often depends on the mix used, as that can create strange effects if not done correctly. Music CDs are generally recorded and mastered in 2.0 of course, so two speakers should properly recreate the original recording. For CD music listening I actually prefer two channel most of the time. Now with that said, I admit I also enjoy music in surround, especially music videos, most of which are recorded in surround these days (5.1) to start with and so they sound best as they were recorded, but also are very nice using the matrix decoders also. I actually copy a lot of music videos to DVD-R and the audio is necessarily copied as DD 2.0 regardless of the original soundtrack, so I ususally play them back using DPLII music or Logic 7 music. Using a center channel will help lock in front vocals (if there are any) but that may or may not sound as good as you expect. But of course in the end it is a matter of personal taste.
I should add that if someone prefers a three channel setup they might want to try using the venerable Citation 7.0 processor. It used a proprietary 7.2 surround decoding process called 6-Axis designed by the legendary Jim Fosgate (who designed DPLII) and because the 7.0 did not digitize the front three channels for it's analog processing, it provided an unusually clean and transparent sound quality. I used the 7.0 for many years and enjoyed it immensely, especially it's two channel bypass, but also it's unique surround for music. For anyone serious about music in surround I highly recommend the 7.0 be given a try, and good used versions usually sell for about $400.