I am incredibly impressed with the Synergy upgrade. I don't know if there's an engineering explanation for it, but I am getting deeper and more realistic bass than I got from the Insight+ amp, and I thought that amp was very good. I also appreciate Frank's observation that this amp is smoother and more musical than any solid state amp previously available from AVA. On my system (T8+ preamp with Mazda 6CG7 tubes, Vision EC DAC, Theta Data Basic Transport, and custom Salk speakers with Heil Air Motion Transformers), there were times when some instruments seemed a bit edgy. I'd notice it in particular on something like a soprano sax or a clarinet when stretching for a high note. The Heil AMT's are probably contributing something to the harshness, but it is much less apparent with the Synergy amp.
I already had a very wide soundstage due to the bi-polar design of the Heils, but the soundstage seems a bit deeper somehow. That might be my imagination, and it is difficult to do an objective comparison when the original amp was out of commission for three weeks while being upgraded. All I can say is that I am satisfied that it was money well spent.
My thanks to Frank and company at AVA!