I was stuck on the assumption that real stereo was pure only when played on two channels. I bought my center and surrounds for home theater use. But Alan's advice has opened my ears, and I now use the H/K Logic 7 as my default setting for stereo music.

I don't think I will go back to "pure," two-channel stereo. The sophisticated soundstage produced by Logic 7 -- as well as Dolby PLII, but I prefer Harman Kardon's method -- is actually a more "pure" reproduction of orchestral performances.