Curiousgeorge, hi I had a pair of these, great speaker, very unlike your typical Klipsch sound, more audiophile quality rather than quantity.
I would look at high biased class A solid state amps power or intergrated. Like Pass, Krell, amps that run nice and toasty.
This will ensure you get that class A high frequency smoothness coming from the Klipsch's tweeters and mids, yet still have the control over the bass with good solid state amp damping factor and dynamic punch.
Cheers George