Prima Luna Dialogue series, is it worth the money?

Personally I don’t think so. Both have :- SoftStart & Adaptive AutoBias, However I don’t think the Premium has UL/Triode switching, not sure? Running in Triode mode can sound better on some valves. Down to personal taste.
You May get slightly better transformers on the Dialogue & maybe better valves, but I think you’ll find they are still the stock Chinese Shuguang’s, which you’ll need to change, if you want the best sound.
Remember a Valve amp’s only as good as the valves you use in it ! The Shuguang’s are cheap get you up & running tubes. Yes I know they have PrimaLuna stamped on them, but trust me their made by Shuguang!
You pay’s your money & makes your choice! Good luck.

I have two Prima Luna amps in service since 2005. The PL 5 power amp in one system and the PL 2 integrated amp in another system. For the last few years, I have been using either EL 34 or 6CA7 power tubes, new production from Electro Harmonix or Mullard. I prefer these tube types to 6550 or KT 88. For preamp tubes, I have been using NOS Mullard.

I enjoy these amps tremendously. I have never wanted to upgrade. When I need to replace them, I will buy Prima Luna.

Until the last year or two, it was pretty difficult to do comparative auditions of the different amps in the PL line. There were not that many dealers. I purchased my PL amps directly from one of the founding PL fathers, Kevin Deal of Upscale Audio.

And that would be my advice ... read the reviews as there are many of them out there and then call Kevin and ask him. He is a straight shooter.

Rich

One interesting thing about the tubes - the stock ones are not necessarily low quality. I did replace the KT-88's in my Dialogue 2 with some EH EL-34's, and greatly preferred this. However, I had a stock AU7 go out on me and bought a relatively inexpensive replacement, and these do not sound quite as good as the stock ones did. The AU7's have the least effect on the sound, though. I have never experimented with the AX7's as of yet.