"Best" Matchless Chieftain?

Try 'The Chief' which is one of the Kemper factory profiles. Perhaps legacy at this time, but definitely available.

If you haven't tried Tone Junkies Match Chief, you should definitely check it out. It's my go to amp.

Tone Junkie's Match Chief meets every point I expect from Kemper. Dynamic range is so good on this pack. You can almost clean out by touching the strings gently and it can really scream if you hit aggressively. I love it so far.