The Dyna-vs-Mac comparison is of course one that has been around for decades but it's one of my favorites!
There are SO many levels to this purely in the circuit design - the Dyna uses an input pentode, the Mac has an all-triode driver design. The Dyna uses a tube rectifier, the Mac uses solid-state diodes. The Dyna uses an Ultralinear output stage, with mainly global NFB from the output tap, and the Mac uses a "Unity-Coupled" output stage with both local NFB and global NFB, derived around different transformer windings. Both Dyna and Mac are rightly renowned for the quality of their output transformers, but the way they're wound represent very different design philosophies. And for the most part, each of the above approaches has a similar level of merit.
Then you get into the economics, how much of the (customer's) money should be spent on each part of the circuit? What are the cost tradeoffs in reliability and sound quality? How long is the product supposed to last, and how much maintainence/repair can be expected? Again, the Dyna and Mac amps are wonderful examples of two very different ways to treat these questions, but each IMO equally masterful.
But I rant. Specifically to your situation . . . I feel that most of the shortcomings of the Dyna's design will be much less apparent with a pair of La Scalas than with direct-radiating speakers . . . when you really drive the amps hard into a demanding load, a Mac 275 will absolutely flatten the Mark IIIs. But the Mark IIIs are still really nice . . . and believe me, you're not the first person to prefer a Dyna to a Mac . . . they're both true classics, in the best sense of the word.
There's also a bit about the MX110 . . . its output impedance is pretty high, and somewhat volume-control dependent. It isn't a problem when coupled to an original 275, but IIRC on the newer versions with balanced inputs, they dorked around with the input impedances for the unbalanced part . . . and I think its somewhat lower.
The Mark IIIs (if original) have a 470K input impedance, which will ensure that either the MX110 or the PAS is doing its absolute best.
There are SO many levels to this purely in the circuit design - the Dyna uses an input pentode, the Mac has an all-triode driver design. The Dyna uses a tube rectifier, the Mac uses solid-state diodes. The Dyna uses an Ultralinear output stage, with mainly global NFB from the output tap, and the Mac uses a "Unity-Coupled" output stage with both local NFB and global NFB, derived around different transformer windings. Both Dyna and Mac are rightly renowned for the quality of their output transformers, but the way they're wound represent very different design philosophies. And for the most part, each of the above approaches has a similar level of merit.
Then you get into the economics, how much of the (customer's) money should be spent on each part of the circuit? What are the cost tradeoffs in reliability and sound quality? How long is the product supposed to last, and how much maintainence/repair can be expected? Again, the Dyna and Mac amps are wonderful examples of two very different ways to treat these questions, but each IMO equally masterful.
But I rant. Specifically to your situation . . . I feel that most of the shortcomings of the Dyna's design will be much less apparent with a pair of La Scalas than with direct-radiating speakers . . . when you really drive the amps hard into a demanding load, a Mac 275 will absolutely flatten the Mark IIIs. But the Mark IIIs are still really nice . . . and believe me, you're not the first person to prefer a Dyna to a Mac . . . they're both true classics, in the best sense of the word.
There's also a bit about the MX110 . . . its output impedance is pretty high, and somewhat volume-control dependent. It isn't a problem when coupled to an original 275, but IIRC on the newer versions with balanced inputs, they dorked around with the input impedances for the unbalanced part . . . and I think its somewhat lower.
The Mark IIIs (if original) have a 470K input impedance, which will ensure that either the MX110 or the PAS is doing its absolute best.