Cornwall IV vs. Volti Rival, Razz; Razz v. 1, 2, 3 -- what changed?

Looking for efficient speakers. I had the opportunity to listen to a Cornwall IV yesterday. It was run on nice tubes (Primaluna 400 EL34s) with a bluesound node streamer/dac.

QUESTION: I'm curious if anyone has compared CW IV with Volti Rival of Razz. Thoughts?

QUESTION 2: Anyone know what changed in the Volti Razz when it moved from v. 2 to v. 3?

Thanks