My wife has a conrad johnson cav 50 in the computer room matched to Reference 3a speakers. She rolls extensively (4 EL 34s, 2 6sn7, 2 12ax7 and 1 12AU7). She really likes CED- Svetlana EL 34s (although she has been known to run Red glassed JJs during the Christmas holidays) and alternates the 6SN7s between about 6 different ones (6SN7Gt Syvania VT 231 in 3 variations) GE 6sn7GTA, Tungsol, Kenrad, Rca GTAnyway (I should probably let her answer this thread) the difference in the tube complement from stock is rather astounding. This integrated is a natural for rolling because it is easy to bias (LEDs) and with the front cage off everything is exposed and easy to get at and it can really sound different with different tubes. The other good thing is that conrad johnson has outstanding service which is also reasonable.
The Reference 3As are outstanding speakers and I highly recommend them.
I'm sure others will chime in; this is just my opinion.
BTW, I use a Zen Decware SET El83 based amp (about 1.5 wpc) in the music room. I roll no tubes. We don't roll the tubes in the big rig in the living room either (Audio Research CL 120 monoblocks- 16 6550s and 4 6cg7)/ Audible Illusions Mod 3A/ 4- 6922 (she did install 6h23n russian for the sovtek 6922 because the sovtek has so much tube glare and the 6h23 is as rugged but much sweeter).
Sorry to go on .
Hope this helps.