jap: I ordered Amperex 6922 and Telefunken 12AX7. Goal here is system matching and personal preference. I'm using Amperex 7316 in my preamp, which, combined with the rest of the system, gives me the sonic signature I like. In my system, the Romulus sounds slightly different (see my comments above), and I am seeking a bit more delicacy and air in the upper midrange and high frequencies. Example: my TT rig, when playing a top-quality classical recording in a big hall, reproduces cymbals and percussion about 25 feet behind the left speaker (where it should be), with the delicacy that conveys the ambience of the concert hall. The Romulus puts it about 20 feet behind the left speaker, but with considerably more emphasis. More than just 'louder', it is more dominant in the profile of the music, and it loses a bit of delicacy that my analog rig conveys. From another angle, the Romulus with stock tubes is heavier in the midrange and bass than my analog rig, and I expect that the new tubes will alter that. I prefer a well-balanced 'profile' of music, where the highs/mids/lows get a naturally balanced sound. My analog rig has quite a nice balance, although the Amperex 7316s do dance/sparkle a bit lively in the upper registers (but definitely not bright in my system). The Romulus stock tubes cause the highs to be less prominent than mids and bass, which causes this slight mis-match in the sonic profile.
Now, nothing says that the CD was produced with the same care as the LP and would ever sound 'the same'. But I am just trying to obtain the most similar sonics that I can achieve, which tells me that I am really, truly happy with my analog rig, and these direct comparisons give me exactly the right scenario to attempt it. I am trying hard in my above comments to bring light to the minor differences, so that folks can get an idea of what I'm hearing. But remember, I am putting this under the microscope for those purposes, and the Romulus sounds damn good. Those folks who listen primarily to vocals and straight-ahead jazz might prefer the stock tubes, as they add a little meat to the bones of the playback. But my ultimate test is complex classical, and that is what gives rise to my comments.
One last thing: My Romulus still has only 100 hours of play and is far from the mfr's published break-in point. And, after reading my comments above, folks will realize that I'm picky about differences in sonics. But my message here is that even with the comments above, I have a hard time NOT listening to the Romulus! It is soooo nice. That bit of 'butterscotch' in the sonics is the thing that most tube folks adore, and yes, it is a bit intoxicating. My system has the perfect balance of all the sonic traits I like, and I'm just trying to cut back a bit on the butterscotch for the sake of system matching all around. I hope that helps.
