I have had at home 4 out of 5 AA Capitole players (and owned 2 of them):
Capitole mk II
Capitole mk II SE
Capitole Reference (which really should be called mk III)
Capitole Reference Signature.
"SE" on the old model and "Signature" on the new model is the same modification. Only name is different. It consists of cap upgrade (SE/Sig models use ultra expensive teflon V-Cap capacitors vs Hovlands found in the cheaper models), cryo-treated tubes and some damping pads under the caps.
IMO, regular Capitole mk II vs regular Reference is a close race. Same goes to Capitole mk II SE vs Capitole Reference Signature.
Now, regular vs SE/Signature, is a different story. No mater if you compare the regular Capitole mk II to Capitole mk II SE or Capitole mk II to Capitole Reference Signature, there certainly IS a very substantial difference.
Having said that, IMO Audio Research Reference CD-7 CDP is much better player than all Capitole players, and is now cheaper as well.
I went from Capitole mk II to Capitole mk II SE, then MBL1531. Now I have CD-7 and could not be happier.