I'll probably keep my Quad and set something with more presence at the lower levels...Oooops -- I just now realised you have Quad 57s!
With all due respect, and good as the Extrema may be (enticing sound; acceptably balanced reproduction across 100-10kHz; realistic rendition of string instruments and most voices), they are really no match for the realistic & pure mid/upper-mid range of yr Quads. The Extrema can play somewhat louder without fear, & offer a modicum of dynamic impact you can't have with the Quads -- but that's it. (I had Extrema for years, years ago).
I strongly urge you to keep those spkrs & invest some fun in identifying something that's a "Quad" with lower end + highs + better tolerance to dynamic abuse! I would also join you in forgetting about technological advances -- your '58 Quads are technologically OK, very contemporary if you will. If you want "avant-garde" spkr components, try Ion tweets: that should get you firmly in the '60s if I'm not mistaken. The B&Ws, etc, are still rooted in the '30s :)! Regards