Richard,

   I think the real question here is: what makes something "vintage?"

   Gear from the 60s and 70s is definitely considered vintage, even if some of that gear is complete garbage. (Think of some of the old Japanese wah pedals with built-in sirens, or even some of the early Electro-harmonix stuff). I have an early EHX LPB-1 that plugs into the guitar jack, then you have to plug your guitar cable into that. Total junk, but a guy offered me $600 USD for it.

    My Strats from the 80s have been considered vintage, probably because they were made while CBS still owned the company, (even though people still poo-poo about the guitars made during that ownership). Go figure.

    My GK 250ML is considered vintage. Is that because GK no longer makes guitar amps anymore?

  So, what does all this add up to? Does it mean that if you label something as "vintage," you can now jack the price up to the moon? 

Dante,

   The 1st one on the order looks right, but I'm not so sure about the second one. There is an extra digit there that concerns me IRF530(5).

   Is there only one brand to choose from? I might go with one that is a little more pricey if it means it will last longer. I haven't looked on the site for quite a few years, so I'll have to go check after typing this.

   I'm not sure it that goo is dielectric grease. I guess it could be, but all the dielectric grease I see these days is more milky looking. Does it smell like grease?

   As for your last question, I have no answer. All my MT100s failed on one channel even after repairs. That's why I posted the question decades ago about the cause. I was wondering if running it in bridged mode had something to do with it.

My ADA gear is obviously getting old but still works well.  There hasn't been anything since that is as good (for me) or I'd consider modernising.

No need to modernize. You can thank the Youtube kids for hyping up the ADA preamps because it's highly desired right now, even in the age of modeling processors.

Richard,

You're not kidding, but I can't use them anywhere but outdoor gigs 

I'm not giving myself any limits. If I'm 100 years old and in a wheelchair, if I have an opportunity to get onstage, I'm there!

You can see the Advanced Tube Tech TA '70 power amp in the picture: it's the first unit on the bottom of my XMas Tree!

Yeah Peter, it is.

It's nice to get on a stage while I still can, I give myself about 10 more years

Love the playing and the guitar 

Good to be playing again, right 

I have 10 split stacks.

Now there's a back line  .