I am just using the stock tubes that come with the Evo 400 preamps and amps. I have not noticed any sibilance, but I will keep your advice in mind if I do notice any.


I would love to hear the PL amps with better wire from the transformers to the power tubes. Now that would be one way PL could make a massive improvement in sound quality. In fact, it's the only way I can imagine these beautiful sounding amps being greatly improved. Van den Hul SCS-12 wire (or SCS-16 at a pinch) would do the trick! Please PrimaLuna?
The Prima Lunas (and I'm sure the Etna has more than a little to do with it) are exposing extremly subtle details in my favourite recordings. In one track that I've played hundreds of times in the past, there is tremolo on the rhythm guitar that I could not hear before. Extremely subtle, shimmering dynamics now fully revealed which were previously lost in the haze. The PL Evos are very seriously good. I'm comparing to my previous Audio Research gear (D250, VT100, SP10). In comparison, the PrimaLunas get right out of the way and you're generally listening to the source, and forgetting the amps. 
On paper these don't seem to have major improvements over the Dialogue series. However, the price sure went up. I'm wondering if by creating a new model they also get a new round of reviews in the HiFi media, which is the lifeblood for sales. If they just increased the price of the Dialogue you get negative press. However, if you create a new model, make a couple improvements, you can justify a price increase and get a round of new favorable reviews. I'm saying this as a big fan of Primaluna and owner of a Dialogue One integrated. Curious to hear from people who upgrade from the Dialogue to the Evo and what they find. I'm sure it's going to sound great, but worth that price increase?
Audio Video Therapy in Nashua NH is having their annual spring audio show May 17. Anthony Chiarella who represents Primaluna and EAT will be there to demo the new line of integrateds.