Charles, I'm with you.
I didn't think I could find a 300b amp that I didn't like, just some "more" than others. Well I did and it wasn't a cheap one. It was a brand new pair of Cary 300b SE Signature mono blocks.
I own Cary 805 AE's which I use to power my Magnepans and love them (yes, it works and works really well). For my hi-eff system I thought it would be a no brainer to get their TOTL 300b. Turns out it was a "yes" brainer. I used their supplied Chinese 300b's to break it in but it never sounded good. No matter what brand of tubes I rolled in, it never sounded right. In fact, it red plated my Sophia Meshes in 5 minutes. That was the clue that led me to finding out that they drive the 300b with 450 volts and 80 mA. Why????? Only they can explain. What I know is that even if they can get 15 watts of power out of these, if it sucks....what's the point. IMHO of course. fwiw, the amp had no bias adjustment so I took it to my tech and had him install a resistor to drop the bias. He got it down to the low 60's and it still red plated the Sophias and it still sounded bad although maybe slightly better than before.
For the OP:
The EH is a good basic 300b. Moving up the ladder...I like the Genalex a little more, the Sophia mesh a lot more and at the uppermost the EML Solidplate and Meshplate. The meshes do not want to be ran hard. There is less plate to dissipate (did I just make a rhyme?) so you will want to find out the specs of your amp before trying them. If your amps do run the tubes hard, I would highly recommend the EML 300bxls. That tube could last easily twice as long so divide their cost by 2 and maybe they aren't that expensive.