"Best..." is a relative term; system compatibility is the ultimate goal. Another "best" might be a used Classe' DR-9 or DR-10 (sold as the Ten in script on the frontplate). They were very conservatively rated at 100wpc at 8 ohms. I've owned them with ribbons, planars, cones--big, medium, small and DRs sound excellent with all. They run $1000-1200 when you can find one. My final Classe' was the Ten (DR-10), that gave much satisfaction with various tubed preamps driving ribbons, planars, and lastly, the Avalon Arcus. The legendary DRs were designed by Dave Reich before leaving Classe' in the early 90s. Do not compare Reich's amps with later Classe's; in the opinion of many I have spoken with (myself included after auditioning later series, including the newest), they are "coarser" than the DRs. There are also a number of other excellent used and new pieces available, but take the time to audition in your system, at length. Your ears only are the final decision maker.
