I got a pair of the later version of the Aquarius 4, it was named the S2.
The S2 was produced in the 80's and has an 8" Driver, and 4 small tweeters in each cabinet.
The S2's that I have do not sound as good as my other multi-directional speakers.
I believe the original version "Aquarius 4" is more collectible, and has higher quality drivers. It may also sound better, but I have never heard it.
The later s2 that I have does not seem to be very efficient. I feal that although it does disappear easily do to it being omni-directional design, it does lack in range. I know it was designed to be run with a subwolfer, and I have never tried it with one.