Depends on the speakers you are driving. Are they a simple/steady 8 ohm load or do they swing mercilessly from 12 ohms to 2 ohms?
John Gale used the B&K's in his May 1999 review of the Thiel CS2.3 Loudspeakers in SoundStage! magazine:
"When the CS2.3s were first installed, I drove them with some aging B&K M200 mono amplifiers, rated at 200 watts each but certainly not current powerhouses. The performance was certainly presentable, but a relative softness in the bass and a sense of "topping out" in the dynamics left a nagging feeling. Inserting the Bryston 4B-ST amplifier (review in the works) dramatically changed the presentation. Dynamics, coherency and imaging all improved under its control."
While this really doesn't tell you a lot about how they will compare to the Monarchy's, it may imply a trait of the M200's. Of course, any relevence to you is reliant on how your speakers compare to the Thiels in difficulty to drive.