Hard for me to keep straight all of the various matrix-based "surround" encoding technologies that Telarc was experimenting with on these mid/late 1990s CDs,
@Imbobman : there was plain-vanilla Dolby Surround (a/k/a/ Pro Logic, which evolved into Dolby PLII, PLIIx, and PLIIz), "Circle Surround," originally developed by SRS (there's a thread on this somewhere), and then the "Spatializer" circuit. (See Brian's initial posts in this thread.) One of the engineers here could speak to this with much more authority than I, but I think they were all roughly compatible and all used similar psycho-acoustic principles to create their wraparound "3D" effects.
You've already heard the consensus opinion: the transport you use for playback doesn't really matter. These are just regular RBCDs with surround "encoding." The Surround Master seems to do a great job decoding all three, but short of that, engaging the PLII DSP on your older AVR will work just fine. (I think it's still possible to pick up cheap secondhand outboard "Circle Surround" decoders, too, if you're really keen on that sort of thing.)
I have two of these Telarc "SurroundSound" CD's, both of them P.D.Q. Bach titles. One is "enhanced" with Spatializer only, the other with Spatializer
and Circle Surround. The booklet for the latter claims you can get a "three-dimensional listening experience" from both technologies using two stereo speakers only and no special decoding equipment. But to "fully realize" the
Circle Surround experience, it adds, "use of a Circle Sound decoder and a properly set up surround system is recommended." That said: the booklets emphasize that both Spatializer and Circle Surround are also "fully compatible" with Pro-Logic. I can attest to that. Neither of these discs is any great shakes, surround-wise, IMO, but PLII does make them sound more spacious, and once in a while there's even the illusion of some quasi-discrete activity out of the rear channels.
You've already had a look at the relevant sections of
@Mark Anderson 's
Surround Discography, yeah?
http://www.surrounddiscography.com/dolby/dolbyanth.htm
http://www.surrounddiscography.com/circle/circdisc.htm