Whip, in one sense(which happens to be the one I most often use)all music with at least two channels was "mixed in surround". Surround ambience from directions other than the front was picked up by the recording microphones and became mixed into the front channels(there was no place else to go). Modes such as DPLII or Neo:6 extract this content and send it to the surrounds where it belongs, making the overall effect more spacious and realistic.
This can't duplicate the total effect of an actual multi-channel recording you'd like where an instrument is discretely placed in a surround channel, but nevertheless, even in pop recordings thought to have little "natural" ambience I've experimented with, the effect was nearly always clearly audible and helpful. For example, I gave a listen now on Amazon to the "Fear of a Blank Planet" sample, using both DPLII and Neo:6, and found both to be effective. Switching the surround off suddenly to stereo mode clearly collapsed the sound field toward the front.
So, if you've listened to this material only in stereo, you might try a surround mode to give you part of what you're looking for.
