I listen to about 99% classical music, and very few labels use the rear channels for actual instruments--they just reproduce the hall acoustics, which is the way one experiences live classical and most rock. I don't recall hearing instruments coming from the rear when I saw Jimi Hendrix, Deep Purple, Black Sabbath, etc.! (Never got to see LZ live.) Now, Emerson, Lake, and Palmer did use surround sound when I saw them in '74, but that's a rare exception. For the record, I can hardly stand 2.0 for classical music these days.
DALI Epicon 2 speakers; SVS SB 13 Ultra subwoofer; PrimaLuna HP integrated amp; Esoteric K-03 SACD player; Oppo BDP 105 SACD/Blu-ray player; VPI Scout 1.1/Ortofon 2M Black; Audeze LCD-XC headphones