I upgraded to the ML-53's from the 33H and they are an improvement both in power delivery, resolution, and do not run as hot. But sound wise they are cut from the same cloth. You should have the 33H's serviced at some point since they were manufactured a very long time ago, and it will cost you $$$$. But they are excellent and have a lot more current delivery than the 150W/CH rating. And they are heavy! Pick them up with a friend to help you. Madrigal hit their peak when these amps were made for audiophiles with demanding speakers (read-Wilson with low impedance curves). Of course the 33's are even better but were hard to manufacture due to high demand (by the super-power freaks). The 300W per channel and a 220V outlet was std. Good luck with that. Of course Boulder still insists that you do that even now... I like the 53's just fine, so no offense to Stereophile Magazine, but I have extensive experience with both amps. You can have your Dartzeel $150,000 amps. Nothing short of a hand-built tube amp with all silver wiring should cost half that much...