I never owned one in my possession but did build 4 for my audio buddies. I also do recommend you to read from bottom to top.
My time spent with them revolved around (in order of preference):
1. Psvane 12AU7-T Grade A: When people hear about Chinese and Russian NOS tube's, almost automatically they think it's rubbish and not as good as the USA and European counterparts, this is not true. Even with the stock generic Chinese and Russian 12v and 6v based tubes you find in many cheap tube amp's online, these may not sound the finest but they sometimes sound better then some of the cheaper old NOS RCA and Sylvania's. The Psvane 12AU7-T tube is the best 12AU7 tube I have owned and heard to date (do note these blow the vintage and expensive 1950's Genalex Gold Lion's out of the water), these are also the best and finest 12AU7 tube's the Chinese has to offer. Similar to the Sophia Electric tube gradings, Psvane offer's 3 grades, Grade A, B and the regular 12AU7-T with the Grade A about $5-10 more expensive then the Grade A Sophia Electrics. I also do recommend those interested to buy from the Psvane website and not on ebay, as I discovered most of the $70 or so dollar ones on ebay are regular or Grade B 12AU7-T's.
Ok now with the sound, the Psvanes sound very similar to the Sophia Electric's except the reason why I ranked it first is because, once you listen to one in an properly implemented tube amp, their is more emotion and realism to the sound. The few moments I was listening to some 24bit Beethoven Symphonies, there was a few times I heard the instrument move and make a swish noise as if the instrumentalist moved in his seat to get his instrument ready for the next piece, it sounded so real that the few times this happened, I looked around in my room to see if someone was behind me (was using my HD800's). There is nothing bad I can say about the sound at all, but if I was being nitpicky I would say that I would love some more rumble, but this is with the HD800's and I'm just being extremely picky to see if I can grab any bad things out of it, which I really can't. To sum up overall with this tube, I highly recommend it, I think they also offer the buy 1 pair, get 2nd pair for free deal as well, but I'm unsure you can check with the website for more info.
2. Sophia Electric 12AU7 Grade A: Still in production by Sophia Electric, a company based in Washington, they also specialise in integrated amp's as well. Probably one of the best currently in production 12AU7 tube you can buy today. There are three grades to their this tube that they offer, Grade C being the cheapest, Grade B and A being the best and most expensive. I bought these Grade A from ebay, bought myself a pair for $100 incl shipping each, and they sent me a bonus pair as well, so have 4 in total but I dropped one by accident and sold the other 2 to my mate's that I had built the Sunrise amp for. These tubes combine all of the qualities of the tubes I listed below into one tube. It's like it adapts and transforms it's sound to match what source and headphone you have, extremely pleasing sounding and a lot of wow factors for sure. I could not find any flaws with sound that this baby produces, throwing rap, electronic, classical, rock, metal, American pop, and some Russian song's, these tube's sing. The only reason why I ranked it 2nd to the Psvane's is due to it's slightly shelved holographics imaging, 3d realism with the Psvanes I can pinpoint things better, if I was listening to Best of Beethoven Classics, piano concerto #11 I have a better sense of hearing various positions of the instrument's playing without sounding uneven but coherent as the piano is playing in the right position being the center of the piece. The Sophia's are a slight notch behind this.
3. Vintage Telefunken 1960's ECC802 Smooth Plates: Ranked third for my preference, these can reach extremely expensive prices due to it's rarity, sometimes over $550 on ebay for a matched pair but you really need to try your luck sometimes (here's a price figure on 4 matched tubes http://www.ebay.com/itm/4-x-BALANCED-NOS-NIB-Telefunken-ECC802S-6189-E82CC-12AU7-ECC82-dual-triode-tubes-/270980448075?pt=Vintage_Electronics_R2&hash=item3f17b17f4b).
These sound pretty good, actually very good with almost all genre's I throw at it except electronic based music. Sort of lack's the bass presentation of my Amperex's but yet again, I like my bass, while you may not, but I'm no basshead. Treble is lush and smooth, soundstaging has an airy feel to it, listen to some Opera or Symphonies and you be surprised at how well the high's is controlled with this tube. I would easily rank this tube as tie 2nd position to my Sophia Electrics but due to its extemely commanding prices due to it being so rare since it's a premium European based tube, I put it as 3rd.
4. Vintage 1960's Amperex (Made in Holland Production line for Harmon Kardon) O getter, Black plates 'Flasher' 12AU7: There are a fair amount of Holland produced Harmon Kardon 12AU7 tubes but most of those were later productions and most of them were produced for Hewlett Packard that was rebranded as NOS Harmon Kardon. It's called the flasher (as well as some Holland Mullards) because in some 12AU7 tube amp's, if you turned the amp on, you would flash blue for a few seconds, unfortunately I none of amp's (including the Sunrise) exhibited this behaviour. I ranked this tube and vintage Amperex CV491's both as equal 4th preference due to it's bass and soundstage.
This tube pairs extremely well with neutral to brighter headphones such as the HD800's, Grado and Alessandro series, the tube add's in bit of fun factor to the sound. To my surprise this was the only tube that cured the slightly edgy bright highs from the Beyer DT990 600ohm's headphones when I owned them, this tube is extremely good with classical/waltz, sometimes my some of Beethoven Piano concertos can sound bit too bright and sharp sounding, the flasher 12AU7 sort of relaxes those bright treble, can be sounding bit dark at times, but bass and the soundstage is what I really like about this tube.
4. Vintage Amperex 1950-60's (not 100% sure) CV491 Long grey plates: The CV491 tubes were sort of a premium line of the European EC822? tube's due to tight production rules since it based produced based on military specs. Searching from online, there was only 4 modelled CV491's to be produced? 1950's Brimar and Amperex and later few decades produced Mullards and RCA? Not to sure, but these tube's are sort of hard to find the original 1950's version that is, some cheaper one's on ebay with no logo's branded as C491's are not actually CV491's because CV491's was distinguishable by its long grey plates touching almost the base of the tube near the pin area. With the sound, it is sort of similar sounding to the Amperex 12AU7 flasher listed above, except it sounds more neutral rather than having a darker, more bassier sound presentation, this tube would suit a large range of headphones and genre's but I'm not a huge fan of a neutral frequency response. Soundstage is also sort of shelved which is why I ranked this one below the above Amperex but they are still tie for for the same rank of preference because both has sound characteristics the other does not have.
5. Sylvania 1970's Square Getter, Short Grey Plate 12AU7: I had this tube as the last preference because it has a slightly forward treble range and sometimes a bit bright, I found this tube the best with some metal, rock and electronic and it suited some of my headphones that was slightly bit too laid back in sound sig and bit dark. This tube helped bring out those laid-back qualities. For some rock, metal and electro and almost of all my classical, it was slightly too bright for my ears. It is a very good tube for darker headphones, but due to it picky with source and headphones, I rated this last, because if you had to changed from genre to another or headphone, you would have to tube roll it with something else.
Hope this helped.