As mentioned above, any of the recent Denon Universal players play HDCD and SACD (as well as DVD-A). Buy a modified version, and you're all set.
As for the question, I don't hear much difference between HDCD and redbook CD. The differences certainly wouldn't sway me to buy a HDCD player over another, better redbook-only player. SACD has a more definite difference in quality over redbook than does HDCD. XRCDs, on the other hand, sound quite good in my opinion, and they will play on any standard redbook CD player.
If I was making this decision, I'd buy a used modified Denon from APL or Modwright. One caveat...if you consider a used Denon 3910, be sure to ask the owner if the laser has been replaced. There have been some reports of the laser assembly failing in a few of these machines. The laser assembly can replaced for a couple hundred dollars.
As for the question, I don't hear much difference between HDCD and redbook CD. The differences certainly wouldn't sway me to buy a HDCD player over another, better redbook-only player. SACD has a more definite difference in quality over redbook than does HDCD. XRCDs, on the other hand, sound quite good in my opinion, and they will play on any standard redbook CD player.
If I was making this decision, I'd buy a used modified Denon from APL or Modwright. One caveat...if you consider a used Denon 3910, be sure to ask the owner if the laser has been replaced. There have been some reports of the laser assembly failing in a few of these machines. The laser assembly can replaced for a couple hundred dollars.

