Yes, as I'm currently interested in the integrated Phaethon I of course could not resist visiting the Ypsilon rooms.
In their own room they played on the hefty Hyperions, the new DAC 1000 and new Wilson Benesch speakers. It's always difficult on a show to get what you are really listening to, but I had no complaints at all, I thought the music flowed with ease and sounded just right. I stayed in here for quite some time and enjoyed some good music.
They were also present in the room next door (through a reseller I guess), this was a smaller setup and I think it was the Aelius playing with some horn speaker. I didn't care for this room as much though. Maybe due to the speaker choice, I don't know.
I was a little disappointed that they were not playing on the Phaethon though, but I get it that everyone wants to show off their top performers.
I ended up buying the Ypsilon Phaethon after testing a few other integrated amps at home, it was one of those moments when you plug something in and put music on play and you just realize immediately that this is something else. I've been nothing but happy with it. I could throw superlatives and clichés around to describe how it sounds, but not sure how much that's worth, to me it just sounds right and I like it a lot! If you partner it with great sources it will make those shine at their highest potential. The design and look of both the amp itself and the remote is also top notch! Truly beautiful.
My one minor complaint is that if it's turned off (or looses power) it defaults back to input 1, it's not a big problem and that's also the input I'm using, but if someone was using XLR cables or any other inputs they would have to switch input after turning it back on.
I have no experience with Rockport Avia I'm afraid so can't really say, best is always to try in your system before buying of course.