Hey all,
Lots of good discussion here!
We've played with 6N23Ps, but I suspect our vendor was probably scraping the bottom of the barrel, because all the samples we got were highly microphonic. Other than that, we really liked the tubes. If you can find some good solid examples, go for it!
I'm looking forward to jamato8's impressions of some "non-standard" tubes, (not 6DJ8, but same pinout)--we haven't had time to really go down that road, except with 6N2Ps, which weren't thrilling. Since Lyr is biased with a current source, you can plug in a lot of different tubes and they'll run, but the results are going to vary based on their optimal operating point, inherent linearity, gain, etc.
Oh, and: we're shipping Lyrs again (since the 10th), so if you have been waiting a while, you're probably only a day or so away from shipping. For newer orders, we're running a continuous 4th run starting next week, so we will *finally* be in a stocking position before the end of the month.
Best,
Jason