Tube & other upgrades for Conrad Johnson pv10 pre

Well, I recently acquired a cj pv10 preamp, essentially for the phono preamp. It has a long reputation (here and elsewhere) of providing a classic CJ warm tubey sound at a reasonable price point for those of us who can't budget $1,000++ for such things. Mid-fi territory, I know.

I bought the pv 10 hoping it would offer an improvement in sound quality from the Rega Fono MM preamp I'd been using previously. It wasn't a giveaway price: people really do bid on these things on the 'bay. Everything is working and looking just fine, but...

In my initial a/b comparisons of the two phono preamps (using Joni Mitchell's HEJIRA as my test lp), I am having a hard time telling much of a difference between the preamps. I have the pv10 volume at about 9 o'clock (much louder means distortion, which the Rega would never do). I move around the speaker cables, as directed by CJ, to deal with possible phase inverting issues (not relevant, it seems).

I haven't yet checked the tubes (which I'm told were replaced at CJ factory by prior owner) but everything sounds mechanically ok.

That said, after more a/b work, I'm already wondering (already) about possible mods or upgrades. Any ideas about tube replacements that might take this stock pv10 to a higher level? Or is it all about the caps, etc? The CJ factory sells replacement tubes, but this one already has those and they are working as they should. It's just not bringing the magic yet.

The tube complement is 2x 12ax7; 2x 12at7; 1x 5751.

My goal is for an upgrade of warmth, richness, midrange "bloom," and sonorousness for small group acoustic jazz (mostly) and also seventies soul and hiphop vinyl. I'm finding the sound a little bit thin and even reedy. I want the acoustic instruments to sound more woody and more resonant. I want to hear some of the depth and skin of the bass drum. (I'm already using a REL sub to get more oomph in the bass at the lower freqs.)

The system is what I hope qualifies around here as intelligent and gently used mid-fi:
Rega p3-24 table
Linn Classik SS amp (replacement Rega fono MM preamp)
Vienna Acoustics Mozart Grand speakers
REL t3 sub
assorted ICs and cables: Van den Hul, Linn, Audioquest...

Any thoughts? Pointers?

Please refrain, if possible, from saying "dude, you shoulda spent $1500++ for a really high quality tube phono preamp." I would if I could....
CJ does an upgrade to this unit. First was " A " and I believe that there is a " B : also. Something else to check: I think the line stage inverts phase, but the phono section does not. Talk to someone at CJ, their customer service has always been excellent.
i have an pv10 and a pv12, there is no distortion even at 11:00, it plays better than the pv12 at times. what type of tubes are in there and wait til they break in some. if you are going to do the mods, then you should have brought the new classic model.........
I also had both a PV10 and a PV12 and found the PV10 more musical and with a much nicer midrange. I wanted that sound back and eventually found a PV10AL here on Audiogon and my midrange is back! The big difference between my system and the OP is the amplifier. I use a cj MV75A1 but occasionally hook up a highly modified Hafler DH500. I get the "blooming" midrange with either amp. The detail is sharper with the Hafler. But the two cj's really make the performers live in the room. The distortion you are hearing as the volume goes up is a clue. The cj shouldn't distort at those settings.