I got a pair of telefunken tube a while ago and I use it with LCD-2 rev 2. The result is airy sound and quite large soundstage. However, it is a bit boring and lack toe tapping factor for my taste. So I'm not using it a lot, instead, I'm rotating mullard, rtc and voskhod.
Yesterday, I tried the telefunken to power my HD800 (low serial number if it is matter and no mod). To my surprise, the sound is just perfect. No harshness in the treble, mid is great, bass is impactful, detail retrieval is great, while maintaining the airy nature. Soundstage and layering is as usual for HD800, great.
The tube is not really easy to get and a bit more expensive than the others, but it is worth it for HD800.
Works great with IEMs too - SE535s in my case. Mullards are good and #2 for me, but the Teles are best.