I've heard and owned several ceramic composite cones with tube amps,i.e., the ceramic metal matrix diaphragms in the Infinity Intermezzo 2.6 and Prelude MTS with the Cary SLI-80. With the right tubes, these are glorious combinations. My advice is buy neutral speakers, i.e., with flat frequency response and impedance curves, and adjust "richness" via tube rolling. This approach will give you maximum flexibility with minimum expense over the long term, and you won't be forced to use cables as tone controls.