Far and away my favorite first track to play whenever I change anything, or just to show the system off, is Chopin's Polonaise in A-flat Major by Malcolm Frager on Telarc. I've been listening to that track since 1978 on various systems. It is one of the few commercial recordings available made on a Bosendorfer Imperial piano (97 keys). I've never heard a better piano recording. Just mentioning it makes me want to listen to it.