CAT SL1 - is there enough GAIN using 0.4mV mc??

I, too, used the CAT with a 0.65 mv. output cartridge (a van den Hul Frog). It was fine, but I would imagine that anything lower than that would be a stretch. When I went to a phono stage with better gain (Rowland Cadence), the improvement in noise floor and dynamics was very audible and welcome.

Call Ken Stephens or Marty at CAT and see what they say.