Would appreciate a brief "crash course" on external DAC's. Based on my current limited understanding, I believe you can add them on to a system in order to play HDCD discs, resulting in enhanced audio. Beyond being able to decode HDCD disks, is there any other benefit provided by DAC's? Will regular CD's played on a DAC sound any better, compared to a standard CD player? I assume HDCD is different technology than SACD, with different players required for each (akin to the beta/vhs battle years ago), with the "winner" yet to be determined? And then there's the CD/DVD-A
duel?

Cheers,
Joe