Wow, lots of different subjects being covered here, and all of them are interesting. For the matter of using Quad 57 speakers, I personally like them, regardless of their shortcomings. I've heard the Dave Slagle stacked Quads and dedicated tube amps, including a setup that used two stacks of two per channel (four 57's per channel). I liked the two 57 per channel setup, but, there were other Quad 57 fans who actually preferred a simple pair of Quad 57s over any stacked array. Again, it is a matter of personal preference.
The only field coil cartridges I have heard are the Audio Note cartridge and a Denon 103 that Dave Slagle modified to use field coil magnets. Both are very lively sounding cartridges. My experience with field coils is more in the way of speakers, and I have heard several systems with both a solid state and a tube power supply for the magnets. I was frankly shocked, and somewhat disappointed, that the tube power supply sounded considerably better. I was disappointed because a solid state power supply would be much more convenient--less heat, no concern over tube replacement, and much better voltage stability (the tube supply changed voltage as everything warmed up, and it required more adjustment to maintain optimal sound).