Good point about having a tester. I found out the hard way that some of my “best” tubes were average at best.
Since having a tester I sorted through about a dozen NOS e180f Mullards. They were from a large batch and I have no doubt they were NOS but they all weren’t the same quality. I matched them in pairs and put the ones with the strongest emmisions in my amp and it was much improved. Great stereo image and a great mono image for lack of a better word with mono content.
The original pair was the same , one was shy of min new and one was strong , much better than new so clearly mismatched.
I think it is worth the few extra bucks to have a place like Tube Depot match and screen for low noise. In fact, the tubes I have that are put on an amplitrex or similar matcher are exactly as advertised
This is important with dual triodes like 12ax7 and 6922. Often times the internal sections of the tube are not balanced. It is much more practical to buy from a trusted source that matches than buy a tester for most people
I only bought one because I started playing with rectifiers and antique tubes. I didn’t want my amp or preamp to be the “tester “