JJ power tubes still have a high failure rate so a lot of dealers won't carry them. If you get them thoroughly tested, they should be fine. Eurotubes seems to have a special relationship with the factory and might be getting better stock than others. Great customer service. The one failure I had from them was because of an amp issue and not the tube itself. Yes, I liked the sound quality of the el34 family with the 6ca7 being the ones I liked best. Way better than EH 6ca7. The E34L seems to be the most rugged of the bunch and the KT77 the most extended.
The tubes that are very reliable and surprisingly good sounding were the EH el34. I liked them in my Jolida 3502.