Steve, great post! I would only add a few observations:
1- I'm not a fan of the chassis mounted "paddle" armboard. I have purchased and made several, from different materials, and I have found that a plinth or outboard pillar-mounted arm always sounds better. I have tested this with the same arm mounted in an oversize plinth that allows mounting behind the deck (top position). Always better.
2- Call me a traditionalist but I'm a big fan of Ortofon SPU cartridges. Not exclusively, but mainly for vintage stereo and mono albums these cartridges always put a smile on my face. So I lean towards high mass tonearms like the classic Ortofons, Ikeda, Fidelity Research and the Schick (sort of high mass). Lately I have heard the Pete Riggle Woody SPU model and I was very impressed.
3- IMO, the single best upgrade for a TD-124/301/401 is to replace the crappy, unreliable analog strobe with a digital LED-based unit. This does not make your TD-124 sound like am 80s consumer Technics turntable. It provides steady platter speed control that elevates the sound from your vintage rim-drive deck to palpably better. I like the Keystrobe kits from the UK but there are others. Not expensive, easy to install and just works as advertised.
1- I'm not a fan of the chassis mounted "paddle" armboard. I have purchased and made several, from different materials, and I have found that a plinth or outboard pillar-mounted arm always sounds better. I have tested this with the same arm mounted in an oversize plinth that allows mounting behind the deck (top position). Always better.
2- Call me a traditionalist but I'm a big fan of Ortofon SPU cartridges. Not exclusively, but mainly for vintage stereo and mono albums these cartridges always put a smile on my face. So I lean towards high mass tonearms like the classic Ortofons, Ikeda, Fidelity Research and the Schick (sort of high mass). Lately I have heard the Pete Riggle Woody SPU model and I was very impressed.
3- IMO, the single best upgrade for a TD-124/301/401 is to replace the crappy, unreliable analog strobe with a digital LED-based unit. This does not make your TD-124 sound like am 80s consumer Technics turntable. It provides steady platter speed control that elevates the sound from your vintage rim-drive deck to palpably better. I like the Keystrobe kits from the UK but there are others. Not expensive, easy to install and just works as advertised.