This post might be too late for Minbean now but I thought that I'd post it anyway - I visited the Green Mountain Audio factory in CO & heard the Callistos mounted on Skylan 24" sand-filled stands. The source was a Sony CDR (forget the model #), the DAC+pre was a modified Birdland Odeon-Lite, the power amp was a $2500 stereo Edge & all cabling was Virtual Dynamics Master series.
I can tell you that the Callisto stands up to all the hype that I have read about that speaker! The sound thru this system (modest by many of us' means) was simply superb! The factory listening room was nothing to to write home about but it was treated in the critical areas (ASC tube trap between the speakers + along the 1st reflection points, absorbers behind the speaker) but still the sound was extremely dynamic, transparent, clear & most of all the music had soul to it. Such good sound in such modest settings - to me, it felt that the speaker had removed the speaker-room equation. Common sense prevailed in setting up the speaker (proper separation, correct height, not too close to the back+ side walls & 100 hrs of burn-in) & not much more.
We played a variety of music & the speaker's characteristics did not change, the image remained locked at ear-eye level.
One of the most fascinating things was how much bass that little 6.5" woofer put out! On several notes I could hear it resonate in my chest! Totally unprepared for that! There is a dual down-firing port that is partially responsible for this bass + of course, the speaker engineering. The bass was distinctly ported (vs. sealed) but I'm happy to report that there was no overhang (something I was very antsy about before I heard the speaker).
Even if it is for grins, Minbean, do listen to the Callistos. They just sound right all the way & with any music. A speaker for all seasons!