Nothing was solved but the GIANT speakers put me off the puzzle!I tried the Mundorf Supreme .33 uF in the attenuation and there was very little difference between them and the Kimbers.
I am about to try 10uF Obbligato oil caps from DIYHIFISUPPLY in an amplifier circuit. When funds allow I will order more plus 20uF to try back in the crossover. They're quite reasonably priced.