Quadio

Never hoid of it.

It is just Blu ray discs with surround channels. Gimmick only.
Have said this, small rear channels at low levels delayed by 200 msec or so can add the sense of a much larger room. You can change the delay to mimic smaller or larger venues. This also gives you the sense of the crowd being around you. Fun for live recordings. 

If you want real surround - SACD.
If you settle for manipulated surround, where were you in the oughts when most classic recordings were available free in surround on the torrents?
The Twelve Dreams Of Dr.... was the best.
As trippy as the Dark Side Of The Moon James Guthrie version 5.1 SACD.
Or the torrents of Alan Parsons original quad mix from R2R?

Aside from the fact that these two releases are great by my ears. If there are any DB or Chicago fans out there then you should check them out. SteveHoffman forums has a discussion.

Other than that, my speculation is that a surround system whether sacd, quadio, or X.2, with digital correction like mini dsp may be the panacea for all of the shortcomings discussed here(2 channel).

Fuzztone, maybe I was sleeping during the "oughts"

The difference being a significant amount of $. It sounded gimmicky to me for years and the I tried it out.