I think one had better be sure to replace tubes in the tube regulated power supply in the Ann 40 on a very regular basis...or be prepared for repairs that can get costly! Personally, I would take a pass on a design that utilizes tube regulation.
Audio Research Ref 10 vs 40th Anniversary preamp
I was wondering what the difference in the sound between the Ref 10 and the 40th ? Not much wrote about that. I btw have the Ref 6 but never heard the 10 or the 40th.