Hi Andrew,
Agree that to optimize full range ESL best is still to use high power tube amps..
Back in '80s, was pretty pleased driving my CLSsI & II with VTL300+Ultimate and/or
ARC Classic150+SP11. A buddy now has CLX augmented by a pair of Descent subs,
similarly, he too could not be fully satisfied by just about any SS amps he tried them
with--always finding the resultant a tad lean-ish--perhaps an inherent character of
CLXs?
Soulution700 is one SS which will control panels of your CLXs with an iron grip,
energizing to make them fuller sounding no doubt. But IMO, the Accuphase A200 is
timbre-ly more refined, pure and natural--not quite as obviously powerful in the bass,
but more articulate and goes just as deep, or almost compared to 700, but is deeper
than that of the stereo 710.
Since you currently already own an almost full Accuphase system, why not top it off
with A200 which will probably make best synergy? If thinking tube route, I'd look into
something like the Jadis which is largely known for its brute power, finesse whilst
being fuller sounding than most. Perhaps big VTL Siegfred or ARC Ref750 could make
good candidates as well, but too much heat and tubes, IMO.. ;)