Oh well, I guess I will chime in and yada yada yada a bit. I own a Callisto Sig and these are really tough to find unless you're willing to buy a new unit. The Cabernet seems to be a little more available here but still not so many on the used market like the ARC Ref2, CAT SL, CJ LS16/17, etc. I suspect your gut feeling of this being a longshot is indeed quite high. Perhaps you can locate A'gon members near you who have one of these to get a chance to hear it in your own system. This is what I have been able to do with 2 local audiophiles; comparing different models on these systems has been of great great value to all three of us.
I own A1s, the Io, Versa 2 and I used to run with the Wolcotts but now CATs, so our systems appear to be very similar. The Callisto Sig is a phenomenol match here so hopefully you can borrow one of these. Good luck.
John