I have years of History owning the 57's and have them today in use as a Stacked Array.
The same Speakers are also used both Single Array and Stacked Array in other systems I own.
I have heard them driven by high quality Power Amp's from very low Watts to more than adequate Watts with Valve Amplification, where Valve Selection has been carefully considered.
I have also heard the 57's used with SS Amp's and SS Amp's vs Valve Amp's.
When being demo'd the 57's using a Neurochrome Modular 65, in comparison to Valve Amp's costing 20 x the N'chrome price, I was quite shocked at how impressive the SS Amp' presented an End Sound.
Recently I have loaned the N'chrome and it is resident in my system to be used alongside my Valve Amp's driving my 57's and other owned speakers.
My suggestion is there is a very affordable way to get very very close to the very best End Sound the 57's can deliver and that is to use the N'chrome Modular 65, it is worthwhile learning more.
The Pre Amp need not be too exotic, a Slagle Autoformer has been used on mine for periods and loaned out to be used with others, where the End Sound even though showing a hint of a rich tone has been extremely detailed and right for the 57.
N'chrome also produce a Transparent Pre Amp, as well as Big Bottle Audio, for either of these it is worthwhile learning more.
Monies will be left to make further choices for other devices.