Thanks for all the replies!
@Zd542: I am not looking for an amp review. I have inherited the amp from my brother-in-law (RIP). I do not know what tubes may be in the amp at this point. He and I had similar musical preferences, and a tendency to tinker, so I suspect that 1) the tubes that are in the amp are not stock, and 2) I will like whats in it when it arrives. At the very least, I will have to replace tubes as they go bad and was looking for advice on high-quality replacements, reliable tube vendors, and good sources of background information and in-depth tube comparisons.
@Rodman99999: Thanks for the links!
@Whart: I tend not to seek out the anecdotal, you really need to listen to ______ (fill in any particular component), reviews. Id be more interested in thorough, systematic reviews of a variety of tubes with ratings in a variety of categories. I dont have sufficient background to know what those categories might be. Im on a relatively steep learning curve at the moment.
@Wolf_garcia: Great link! I wish they had my M520 in the Shop by Amp section.
@Buconero117: LOL
Hi, my name is Brian and Im an audio-holic.
@Bajaed: You said it much more succinctly than I did above.
Cheers... Brian