The four monoblock models are all great amplifiers, but each imposes on the system's sound a different character. The Pass Labs XA60.5s excel at soundstaging and image palpability, but lack the iron grip on a loudspeaker's bottom end exerted by the high-dynamic-range Classés; the Lamms' forceful sound lacks some of the MBLs' subtlety, though the 9007s' low frequencies lack a little by comparison in terms of ultimate authority. Which amplifier I prefer has depended on the loudspeaker I'm reviewing.