What are the differences between XRCDs?

SHM uses the original master, only the material used is different/better.

So my Eagles Hell Freezes Over US press < SHM version

K2/XRCD involve remastering so IMHO the remastering accounts for why K2/XRCDs sounds better than the standard master (used in regular press or SHM).

But there are now SHM XRCDs that have the best of both worlds.

ps there is a new K2 Direct Cut that is even more impressive than K2/XR but limited to Asian titles for the HK market.

Here's another good source:
http://www.elusivedisc.com/Home-Of-XRCD/products/859/

I listened to my K2HD Hell Freezes Over last night, very impressive sound quality for a CD.
Also own the K2HD version of Kind of Blue. Of all the versions I've owned this version is the very best, highly recommended!

The 1st generation XRCD (made in Japan) are out-of-print OOP.
Sure, you can find them on eBay or Amazon.

The newer variants are XRCD2 and XRCD SHM...etc.

Happy Listening!

Gold CDs mast be the best of the bunch.