I'd recommend that a non-classical music listener who wants quality classical sound must get a copy of "John Williams Greatest Hits 1969-1999". Those are great recordings that show the full range of orchestral sound, and are mostly familiar to all of us.
I'd add Dvorak's New World Symphony to JohnK's list of great classical compositions to get, and any recording by a great orchestra (London, New York, Berlin, and many others) is worthwhile.
On that note, if you only want a few CDs, spend an extra few dollars and stick to the best recordings on the best labels. The $1-per-CD box sets at Costco are OK for the car as background music, but they're imperfectly recorded by small and not perfectly rehearsed orchestras, and a good sound system would point out the flaws easily.
--Martin
