[Arran]

My MP VI (21 toobs) has a cable which is hard wired to the tuner chassis, but with a plug on the end which mates with a socket (original) on the amp/power supply chassis.

Palegreenthumb, I had forgotten that your MP VI is like Bruce's set. You must send me the link to the video showing your set playing again - I was so pleased that the modern speaker setup I put together worked out so well for you.

 I'm not the least bit surprised that a Masterpiece VI would sound good with a modern P.M dynamic, whilst many electrodynamic speakers sound good they all have one thing in common, a low level, low frequency hum. In spite of what the audiophools believe in this more recent craze there were good reasons for G.E developing alnico 5 magnets and why P.M dynamics took off in popularity after the war, and it was not because they were cheaper. If you look at most British and European radios, once powerful artificial magnet materials became available they dumped electrodymic speakers wherever they could, and nobody is going to say that British made loudspeakers sound bad.
Regards
Arran