Your system sounds really nice. Best upgrade path I would suggest is to switch to an MC cart. Add SUT (like Bob's Devices) or active head-amp (like a Piccolo2). Also try some tube dampers (even simple o-rings can make a difference).
Upgrade phono stage?
Have an AudioNote M1 phono MM. It still delivers great music! I don't know if I should upgrade the phono stage part. Purchase a stand alone phono stage and run it through the aux inputs?
Gear, George Wright mono blocks 2a3 (set)
Audio Note M1 phono MM
Jager Speakers (Bottlehead)
Rega P3
Gear, George Wright mono blocks 2a3 (set)
Audio Note M1 phono MM
Jager Speakers (Bottlehead)
Rega P3