I had 75SE driving Cremona before (as well as Amati Homage and others), 75SE was sufficient as long as you don't listen insanely loud. I took the plunge and upgraded to 150SE, changed the caps, internal hook up wires, and wall outlet. even driving very demanding loads, 150SE sounded tight and fast, a huge improvement over 75SE. midrange and up are of course to die for.
You don't need the "conversion kit" from BAT if you are comfortable with solder iron.
You don't need the "conversion kit" from BAT if you are comfortable with solder iron.