"The only place where biamping makes sense is with subwoofers." Siegfried Linkwitz and owners of older Magneplanars disagree. The .6 and earlier Maggies had parallel crossovers, and a simple 2-way electronic x/o can duplicate the "textbook" stock speaker-level x/o. Those of us who have done it have experienced significant increases in sound quality, for a number of reasons, all well known.
Speaker-level parts are many times greater in value than the line-level ones required to duplicate their functions, with resulting sonic penalties. In their Tympani model owner’s manuals, Magnepan RECOMMENDED bi-amping for maximum sound quality. Having the midrange/tweeter amplifier unaffected by the speaker’s woofer alone can provide considerable benefits.
Seigfried’s excellent LX521 loudspeaker requires four channels of amplification, and Nelson Pass has designed an analog x/o specifically for it.
"IMHO plate amps do not cut." I take it you haven’t heard a Rythmik sub, ;-)