Chartles1dad,
I wish I could compare the RPs to other premium tubes, but my 300b history is: Golden Dragons (came stock), Carbon Princesses, and the RPs.
First, I agree with you that all 300b tubes arent ideal with all 300b amps, regardless of specs.
Many of our peers wince at the word musicality; but that, in a nutshell, is exactly what is so special about these tubes. They offer all of the audiophile characteristics that are important to me, in a balanced, natural way, that brings me much closer to my ultimate goal of suspending disbelief that Im listening to real music. And for those who think enhancing musicality and detail are mutually exclusive endeavors, I think these tubes would be a real illumination.
That said, my amp requires four of these suckers, and I would be delighted to find that I can have RP performance or better, for less.
I hope this is helpful.