i've owned three pairs of 63s including Crosby modified Pros. In hindsight I don't know why I owned three pairs as I never really loved them. Technically they were a brilliant design that incorporated a delay line and sectionalized panels with concentric rings which allowed the speaker to radiate like a point source even tho' its panel speaker.
sonic-wise 63s will play louder and have better frequency extremes . To my ears 63s also exhibit a bothersome 'plastic' coloration that some other 'stats like Martin Logan's can sometimes have. If you look at a 63 in the nude sans grill cloth, you'll see the delay line, its literally a hundred (?) feet of extra wire the signal traverses through. It involves additional complexity/circuitry which IMO impacts the transparency/immediacy of the speaker, here the 57 betters the 63 in that regard. another thing, 63s will need a lot more juice. where 57s can sing with 15-20 watts, the 63s IMO need a min of 100 WPC to wake them up. If you ask Kent what he thinks, he prefers 63s over 57s all day long. The 988 is the successor to the 63 and I think a better speaker.
