Haven't seen a Mission or Marsh, but have seen David Allen's work, and he builds 'em just like the old Fenders, pretty much bullet-proof. I guess Matchless amps are bomb-proof then...
I've played a Chieftain, that's an absolutely astounding amp that truly inspires you to play better, so I can see someone shelling out some serious coin for these amps, they are that good. Granted, it's always a deal of 90% of the tone for 10% of the money, and you always shell out big for that last 10%... I'd say the Allen is about 95% there, Headstrong 97-98%, and Matchless 99.9%... jmo, of course, with prices to match...
Franc Robert