I have a pair of vintage Pioneer HPM-900s that I think sound pretty good. They're in very good condition. I ran across the Janzen crossover upgrade for the JBL Century (which was the launching point for the Pioneer HPM series) and it got me wondering if anyone has done something similar for the HPMs. I have too many other projects to fool with it right now, but someday it might be nice to see how good they could sound with some updated electronics.