Bruno,
I have the CAT Sig Mk3 & have no experience with the Ultimate Mk1 or Mk2. However, I have spoken with Ken Stevens many times & specifically asked him what the Ultimate Mk2 was all about. From what he told me is seems that the main push in the Ultimate Mk2 is: better power supply & an emphasis on getting the timbral accuracy of the instruments & voices just right.
FWIW.
I have the CAT Sig Mk3 & have no experience with the Ultimate Mk1 or Mk2. However, I have spoken with Ken Stevens many times & specifically asked him what the Ultimate Mk2 was all about. From what he told me is seems that the main push in the Ultimate Mk2 is: better power supply & an emphasis on getting the timbral accuracy of the instruments & voices just right.
FWIW.