Tube Amp, Preamp upgrades -- what did you do that improved your units?

@ihcho How about upgrading transformers?

Do Quicksilver amps have high enough quality transformers and they don’t need to be replaced?

No on upgrading transformers. They are good, high in quality and function.  

The bones of the amp, circuit, transformers, sockets, point to point wiring, is solid. Not naming the transformer manufacturer, they are quite good in stock form.  More spec info available in reviews. One of the reasons I bought the amps, powering my larger custom 4-ohm 92.5 db speakers. The amps don’t even break a sweat. Nor do they run hot like many of my former tube and SS class-A amps did.

In my opinion the type of upgrading you are proposing makes sense for someone who is interested in doing the work themselves (DIY) as a learning experience along with hopefully improving the sound knowing that these changes may or may not improve anything and may even degrade the sound causing you to roll back some or all of what you replaced. The big problem with having someone else do these changes is if a number of items change at one time and the sound does not improve and possibly degrades then, which upgrade created the problem? You need to upgrade one item at a time and listen for a period of time to determine what the differences are and if they were worth keeping. Then do the next. This can get expensive if you are paying someone to do this work, which makes me say it is not worth the time and money. If however you are doing this because of a perceived flaw in your amplifier that you are hoping to improve on then I suggest selling the piece and using that money along with the money for parts and labor that you were going to spend and use all that money for another amplifier that sounds better. On the other hand if you love the amplifier then just work on upgrading the peripherals such; tube dampeners, NOS tubes, higher quality feet, replacing power / interconnect / speaker cables with higher quality ones that sound better to you and possibly upgrading your electrical receptacle along with installing a dedicated circuit to power your amplifier. I believe this route has a better chance of seeing noticeable improvements and would cost about the same, depending on how wild you chose to go. The quicksilver line of amplifiers are well thought out and perform very nicely so paying someone to mess with them does not seem to make sense to me.

@axo0oxa Thanks for your caution. It creates some indeterminacy to do multiple caps at once, but if it works, it works big. That's a gamble, and if there weren't other quicksilver owners testifying to the benefits, it would be perhaps too much. But there are and so it's not. I'll let folks know. My mind is made up. 

Good for you!  Only personal experience will allow you to determine whether benefit worth the cost. I expect you'll find the benefit well worth the cost using any of the top flight caps. And aren't all moves in audio taking a chance, purchasing new equipment is as much, perhaps a greater risk. Too many allow fear of failure to interfere with progress.

No on upgrading transformers. They are good, high in quality and function.  

Good to know. Thanks. @decooney