My receiver of choice in the '70s was an Onkyo TX-2500 amp/receiver. It's the only DC-coupled amp that I know of. I could push it full volume through my JBL 4311's without distortion. The Onkyo lasted about 25 years and was replaced a few years ago by an Onkyo TX-8511. I don't think it's DC-coupled though. The JBL's are still going strong. Both are what my M400 goes through.
Bernie
Bernie