Pedrillo,
The Joule OTL-based amps are a horrible match for the Merlins (especially the VZN 80). Not only that, but Jud and Marianne Barber are the worst when it comes to customer service.
Sigh. OK, all of the OTL amps from Joule-Electra are a fantastic match, and the customer service from the husband/wife team is impeccable. You see, I am in the market for a new amp to go with my Merlins and I do not want the competition!
80 watts from the VZN 80 is plenty of power for the VSM. After a lot of research, that is what I am on the lookout for. Just be aware that the newest version is a Mark V.
Good luck hunting!