I have heard both, and thinking about moving to the regular version from my Audiovector R3, I did hear a difference, but not enough to make up for the price in my opinion. Now, that could have been because the regular was driven by a Classe delta stereo, my current amp, and the signature was driven by pass labs, can’t remember the model. But I generally don’t like pass labs.
(it was at a dealer and it was in two different rooms.)