Larry,
I've invested more than many but not as much as Gerry in 300B's over time. I agree with Gerry that the Elrog's were amazing tubes and by far my favorites in my amps. Like Gerry, one of mine died (filament went out) and the other sits in a box. They were short lived, expensive and I too wouldn't buy them again.
I lived near DocB and the team for a few years and would take over my random 300B's and listen to them in the BH system. Doc and I had a lot of fun (or at least I did) doing this. Bang for your buck, there is no better tube than the EH's. BH voices their systems with them and you can flavor the amps with capacitors for cheaper if that's something you're into. Capacitors make a difference and you don't have to spend a fortune on them either.
Currently I'm still using a pair of EML mesh plate 300B's. They sound good in my system and they just won't die. Would I buy them again, yes. They sound better to my ears than the solid plate EML 300B's. Until this pair dies, I have no plans on trying anything else. Most likely what I'll do when they die is put in a pair of EH's and laugh all the way to the bank. The nice thing with EML, they have a two year warranty with new tubes to the original owner. Jac is great to work with and the Euro is quite low now. I would purchase them again from JacMusic without question if I were to buy them again.
The Takatsuki tubes are the only one I would want if I were to try another high end tube. There were some problems earlier on but I've not read anything about problems with their build quality in years. Gerry has a good ear and the experience with them. If he says they sound 25% better, I believe it. You've got to remember that many amps run a 300B hot and burn them out quickly. If you run them at a normal operating point, they are long lasting tubes. I've read of WE 300B's lasting decades at conservative OP's.
If it were me, I would spend money on room treatments and tuning the room over fancy tubes. I remember one time with Doc and the BH system, we moved room treatments and speakers around for a few hours. There can be a dramatic difference with very minor changes (e.g., bass traps, speaker and listening chair placement). Personally I invested in a calibrated USB mic and downloaded the room set up wizard program. If you have a well tuned ear, you don't need it, but I don't and it amazing how one inch of movement can fix a hump or suck out in a room.
If your room is already tuned well, and after capacitors, I would recommend rolling driver tubes. I've got about every 5670 variant ever made. That wasn't enough, so I modified my amps and split the dual triode driver tube. I use a 5670 as the shunt regulator and currently a round plate 7A4 as the driver. It's a damn rabbit hole for sure but if you want to spice things up, driver tubes are a hell of a lot cheaper then 300B's. I like to mix and match. My favorite 5670 though is the GE 5 star and even with all of my messing around with drivers, I'm not sure if my current set up beats the GE 5670.
By far the best thing I ever did for my system was to stop messing with it and just enjoy the music. I've picked up new hobbies and haven't touched my system in literally years, not one change. It sounds good to me and that's all that matters.
I hope this helps some and good luck with your search for 300B's!
Aaron