Quick update to close out this thread. Had a quick 2 day vacation to Portland last week and called EuroTubes before I left home to set up an appointment to pick up a pair of the 2A3-40's while I was down there. Eddie (the EuroTubes tech) hadn't seen a Stereomour in person, so asked me to bring my amp down so he could look it over and take a listen.
Dropped it off on Monday afternoon at their small shop in a Portland residential suburb, and it was clear that Eddie and the rest of the crew have a passion for tubes and tube amps, in the same way that Bottlehead has a passion for their amp products and Blumenstein with their handcrafted speakers. Most of the Eurotubes business revolves around guitar amps, but they also support and enjoy the hi-fi scene as well.
Picked up the amp on Tuesday before heading back to Seattle. Eddie had installed the new JJ tubes and also tightened a couple loose nuts (must've come loose on the drive down in my old vibration-ridden diesel truck). I missed the listening session he had with the amp since I arrived just before they closed, but he gave a favorable review. He also suggested a JJ ECC81 input tube for $16 since the stock tube was measuring 10% out of balance, so I figured why not.
After hooking it up at home to my Orcas, my overall impression is noticeably more definition from top to bottom. Brighter (but not shrill) highs without any compromise to the low end. Bass is, without a doubt, more defined. The JJ's provide a different sound and overall, in my book, a substantial and cost-worthy improvement. The Stereomour with Sovteks was wonderful, but the JJ 2A3-40's have definitely kicked it up a notch. I'm a happy customer. That's with the stock 12AT7 tube and with just a few hours on the 2A3-40's. I'll install the JJ ECC81 in the next few days for comparison.
I'll note that the 2A3-40's have stunning looks, as well. Taller and wider than the Sovteks. Sufficiently elegant such that my wife voiced her approval. The branding is on the ceramic base of the tube, too, rather than on the glass, which I like. With the way the pin sockets are oriented on the Stereomour, the branding ends up facing mostly to the rear, so can't be seen from the front of the amp.
Again, huge thanks to the Bottlehead crew for making contact with Eurotubes to sort out the concerns.
A few photos of the new tubes in my Stereomour below. The ECC81 was installed after the first photo to show the full complement of JJ's, but I haven't listened to it yet.
(https://lh5.googleusercontent.com/-eApTm0g9DB8/VK7ABgR4thI/AAAAAAAACMg/P0qkDJ8tv6g/s640/IMG_9182.JPG)
(https://lh6.googleusercontent.com/-mvkvdi_NCEw/VK7ACKXXl7I/AAAAAAAACMo/PjXzsdZj_TY/s640/IMG_9183.JPG)
(https://lh3.googleusercontent.com/-35SXGj3iJzc/VK7ACRKzy_I/AAAAAAAACM0/41TrIOrgHwA/s640/IMG_9184.JPG)
(https://lh6.googleusercontent.com/-GRHAGYImwHE/VK7ACyZcCeI/AAAAAAAACM4/-lAMl1PZ8g4/s640/IMG_9186.JPG)
