I found remarks about the Melco High Quality Media Library here: http://forum.minimserver.com/showthread.php?tid=2032.
It seems the ethernet connection to the player is optically uncoupled from the rest of the network (but otherwise part of the network). There are also some other improvements that are also described on the Melco web site: http://melco-audio.com.
Could some or all of these improvements be built into a Raspberry Pi setup (at a fraction of the cost of course!)?