I purchased "The Great Cold Distance" by Katatonia, which came with a 5.1 DVD-Audio Disc.
This is the first multi-channel audio I've listened too (other than the DVD concerts of Pink Floyd & Led Zeppelin). It is AMAZING. What a different experience.
The only issue is that it's really only a 4.1 master. There is no center-channel information. Doesn't matter though, with the SongTower's, you'd think the center was playing anyway.
Also, this DVD made me a believer that DACs can sound different.
I have my Oppo 980H connected to my Marantz 7002 using HDMI, Coax & 5.1 analog audio outputs. I can play the DVD-Audio over HDMI or the 5.1 analog outputs (can't use coax because of DRM).
In any case, I REALLY prefer the sound over the analog outputs. For some reason it just seems more balanced.
In any case, if you like metal, I'd recommend you checking out this CD/DVD combo.