Considering 4 12AX7 Tube Types

Sorry,haven't tried them.Another one to consider is Gold Lion.It has the qualities you are looking for and seems to consistently deliver them in many components.My experience has been the mids warm up immediately,the treble is awful and begins to improve at the 20 hour mark.It continues to improve and fully settles in by 50 hours.Best of luck in your search,hopefully someone will post the info. you actually asked for:D

As far as new production goes I agree with gold lion tubes Have you tried any Sylvania 5751 in replacement of 12ax7
As a AVM AUDIO dealer I have tried many 12ax7 in my AVM PA 5.2 pre-amp and have switched to 5751
Good Luck
Dennis

Cheap: JJs - warm and sweet.

old - but awesome: GE 5751 black plate triple mica.

I have the Ruby 12AX7AC7 HG as well as Low Gain Penta Labs 12AX7 tubes purchased from Doug's Tubes and both are awesome sounding with a little bit of differnces. In my Jolida 502P amp with the Ruby 12AX7AC7 HG I got lots of nice details in the mids and highs without any irritation. When I needed a little warmer/laid back presentation in the music I found the Penta Labs 12AX7 tubes were good.

Also with Noromance's recommendation of JJ tubes I agree with his assessment. I got a pair of matched JJ 5751 tubes and in my Jolida I found them to be quite sweet and warm sounding to.

If you are going to go NOS my recommendation would be for JAN GE or Sylvania 5751 tubes. These were NOS tubes I could afford and I found them really sweet sounding vs NOS budget tubes like RCA grey plate 12AX7s from the 70s or yellow label 12AX7s from Westinghouse or Sylvania. With my gear these tubes sounded very thin sounding in the highs and mids.

I've a mini review of this subject in my system:
http://forum.audiogon.com/cgi-bin/fr.pl?vopin&1360528209&openfrom&14&4#14