That’s a lot of $$ for the upgrade.
If I were in your shoes I think I would be looking for a different speaker also. I think the Reference 3A Mm DeCapo or Reflector would be a great choice., but thats my opinion. Also pretty versatile speakers. Will work with everything from 300B SET to Nelson Pass First Watt F6 or F7.
I upgraded preamp and drive tubes and fuses in my Ars Sonus Filarmonia, made quite an improvement. I am thinking down the road I may get the new Sophia Electric EL34 tubes. Also I may have the coupling caps changed out for a V-cap or similar.
If time permits let me know what you finally settle on. I would be interested in your personal experiences with the Fila.