Thanks guys, all very helpful.
Tonally, I guess my priority is a rich, warm but clear, classic clean sound with lots of detail. My main amps are a 65 Amps Soho HP, a Budda SD45, and a Fender Bass Breaker (2x12 Custom Shop Bassman) and I want to optimise the guitar for the Bass Breaker, for rich, piano-like tones. The 57 Classics do sound great, and it would have to be a significant improvement for me to make the change. They get me almost into Gretsch Filtertron territory on the mix position (a good thing!), but they are a little imbalanced between neck and bridge, the bridge is prone to a touch of hardness at volume, and the neck can very occasionally get a little too plummy.