finding the weak link

@larryi : I agree with you! The 6L6 family is my preference for output tubes. I presently have a pair of Heath W5's and a pair of Stromberg Carlson's in use! Along with my Fender Twin Reverb guitar amp (black plate RCA's).

The biggest change the OP can have would be a different pair of speakers. How about some Ohm Walsh's? I have a pair of the Sound Cylinders and OMG do they fill a room with 3-D SOUND! The performers are RIGHT THERE in the room! Ohm in Brooklyn can build a pair of Sound Cylinders in any finish the OP desires!

Oh, I'd like to hear those speakers!

Thank you all for your responses, they are very appreciated!

For those who asked, the remaining details of the system:

Dr. Feickert Volare Turntable,  Origin Live Mk3A select tonearm,  Hana E Series MC Phono Cartridges - EL

MoFi Electronics UltraPhono MM / MC Phono Stage × 1

Tube upgrade:

Brimar CV4003 / 12AU7 (2)

Tung-Sol KT 150

Cables and Power

              Kimber 12TC speaker cables

Audioquest

Sydney (interconnect)

Niagara 1200 Low-Z power/noise dissipation system

Wind series Monsoon power cable

NRG-Z# power cable (2)

Rocket 88 Speaker Cable

Morrow Audio

SP6 Speaker Cables

MA4 Interconnect Pairs (2)

Nordost

Ax Angel RCA Interconnect

Frey 2 Interconnects RCA

No obvious weak links.

You could try going to a separate pre and power amp.