"the 57’s need a fair bit of SS power"?! The 57 was designed to be run with the QUAD amp, which produced 15 watts/ch. One solid state amp which became very popular with the 57 was the Bedini 25/25 (guess how much power it produced ;-), which was capable of overpowering the speaker. As clio said, the Music Reference RM-10 is an ideal amp for the 57, especially the Class-A 25w/ch version.
Add subs for below 40-60Hz and be happy forever. Unless you’re cd318 ;-) . The speaker is not for everyone---you have to be able to appreciate it’s abilities, nor for all music---I wouldn’t try to play AC/DC at 100dB (which I like to do) on them. But for singers and small-scale acoustic music? Perhaps still unsurpassed, and yes, better than the 63, regardless of what Peter Walker thought. But take off those idiotic metal grills!