Here is also from probably the person who's heard the most varied tubes with the unit from headfi thread. So he is considered one of the top 3 people to ask about such thing this is what he told me in PM.
***** Ultron SQ PCC189/7ES8 (DJF V3B, Bharat India, gold label)
***** Amperex 6DJ8 (GAC ⊿9F3, Heerlen Holland, single support leg dimpled disc getter, orange globe logo)
****/ Siemens PCC88/7DJ8 (≠2J)
**** Siemens PCC189 (IP1 B7C3, Mullard Blackburn England)
***/ GE JAN 6BQ7A (USA, green label, o-ring getter with glowing wire under it)
***/ GE JAN 6BQ7A (green label, o-ring getter with glowing wire under it) - this sounds actually very good with metal and is similar to Ultron & Amperex GAC ...BUT it has somewhat loose bass and you don`t get so much bass tightness and kick out of it as with latter ones. Reason why I recommend to try this is because it is very cheap @ eBay. Great starter tube for metal/rock/progressive. But note that there is also version without thin glowing wire under getter. I have the version with glow-wire under o-ring getter.
**** Siemens PCC189 (IP1 B7C3, Blackburn) - This tube is probably re-labeled as Siemens because according to code it`s made in England Blackburn. Mullard PCC189 made in Blackburn should be "same". Try to look for those if Siemens is too expensive or hard to find but note that there are 3 different physical build of them. About sound - it`s better all-around performer than other tubes I mentioned for Metal. Highs might sound little bright with bright-sided cans but still has tinybit smoothed highs.
***** Ultron SQ PCC189/7ES8 (DJF V3B, Bharat India, gold label) and
***** Amperex 6DJ8 (GAC ⊿9F3, single support leg dimpled disc getter, orange globe logo) - These tubes sound actually very similar but Ultron has fraction better bass tightness & kick. Soundstage is "same". I would describe those tubes soundstage as middle-sized soundstage - you get enough air and soundscape but it doesn`t sound so distant. For example I find these tubes littlebit better than my gold pinned Siemens E88CC with metal/progressive because Siemens has so huge soundstage with so much separation and air, that it makes metal lose its "intimacy"... often feels too holographic for metal/progressive/rock genres.
****/ Siemens PCC88/7DJ8 (≠2J) - this tube is basically "same" sounding than Ultron & GAC but it`s somewhat more mellow & warm.
Miniwatt-Dario ECC189 (|X1 ±2L4 .. , Chartres France, yellow "shield" logo) - tightest bass & percussion kick out of my tubes (and it`s deep also) with quite large soundstage
Amperex 6GM8/ECC86 (⊿8J5, orange globe logo) - HUGE holographic soundstage with deep bass (somewhat boomy but I like it with dNb/dubstep/downtemp)
JAN Sylvania 6922 (82219 EAD 7002, US, green label) - good for electronic music with lot of vocals
6922EH ("stock" tube with Aune T1) - Large soundstage (littlebit V shaped), sparkly highs, mids are neutral but after capacitor upgrade it sounds actually pretty good with tighter bass and littlebit more mids.
Great all-around tubes:
Siemens E88CC (GØ 1≠ 6A / GØ 1≠ 5L / EØ 1≠ 6A, grey plates, o-ring getter, gold pins) - expensive and hard to get, very good detail and instrument separation & transparency, sometimes sounds too holographic and too large soundstage for example with rock/metal.
Siemens PCC189 (IP1 B7C3, Mullard Blackburn England) - very good all-around tube, nothing to complain about but nothing wow/special also. Good transparency and separation. Middle sized soundstage. There might be 2 different builds but not sure atm.
Ultron PCC189/7ES8 (50402, white label) - there are at least 3 different build types because this is re-labeled brand. Highs are littlebit smoothed but not so much as Amperex 6DJ8 GAC or Ultron SQ PCC189 and with some metal/rock might feel tinybit bright. With warmer headphones should sound great.
Miniwatt-Dario PCC189 (IP9 ⊿9F1) - Should be quite "bugle-boy" sounding tube but not sure, hard to find with MW/Dario labeling but according to code should be quite easy to find under different label.
Tight bass & kick, middle-sized soundstage.
Note that my impressions are littlebit over-emphasized to bring out differences. For beginner analytical listener differences could be much smaller.