If you had a dozen pairs of classic vintage ubes in your closet

@jjss49, perhaps you should consider that English is not everyone’s first language.  

@jjss49 ,,,  r  u  thinking your English language punctuation and usage of upper and lower case characters is correct?  Perhaps you should use spell check and re-read what you are posting.

Tube Confidence:

This is one of the reasons I suggest tube people buy a simple tube tester. Not sophisticated testing, but enough to give confidence in any NEW or USED tube: no short; decent strength; for pairs, essentially same location in the ’good’ area (not likely to cause balance issues).

here is a simple one

https://www.ebay.com/itm/Vintage-Sencore-TC136-Tube-Tester-with-Manual-good-condition/143927443123?h...

here’s mine

https://www.ebay.com/itm/Accurate-Instruments-Tube-Tester-Model-151-with-157-model-manual/2548323165...

I have a big Hickock, and gave my friend a big Jackson. As far as shorts and strength, the little one always gives me the same answer. Very lightweight, portable, take to friends house ...

make sure you get the manual with tube listing booklet with it.

Also, verify it can test your tube types with seller. Mine does not have sockets to test a few types I have run across.

Whenever I buy NOS tubes I listen to them to make sure they work and aren't microphonic (which many I've purchased have been).  I like to switch tubes around, so they don't sit in a closet unused.

OP,

Remember, new ones need break-in. Brent Jesse told me: Leave on for around 60 hours (no signal required), then compare.

Are you saying listen to spares of the same brand? I would not bother unless I suspected a problem.

If you mean, try different brands, it is fun to satisfy curiosity and learn. I blew one, bought matched pair new 6SN7's for my Cayin, hated them.

Tried some old tubes I had in a drawer (I've got a lot of NOS and used), loved em. Brent Jesse let me return and exchange for new matched pairs of those, and they cost less, gave me a refund for the difference, no restocking charge.

It's not just the power tubes that can make very audible differences.

You can confirm your current choice sounds best, or find something else you might prefer.

Cost: nothing but time (after you buy a toy tester).