Vernneal, I suspect that the earlier posters are correct that you are really asking about HDCDs. Only the Crystal chip set, I believe, plays HDCDs, which have been somewhat lost with Micro Soft buy this format. The original Oppo uses this chip set and does play both HDCDs, CDs, and SACDs. I have never figured out how to force the Oppo to play HDCDs as CDs, but the HDCDs do sound excellent. Many performers want their recording done on HDCDs.
EXPLAIN HD SACDs to me.
I have a player that plays both. Explain these to me. Are they worthwhile