i woodn't be worried about using a solid-state amp w/subs when using tubes on top - wood prolly ackshully be a good thing, considering ya want the subs to be as fast as possible to keep up w/the 'stats.
i tink it inneresting yure using the cls - i strongly considered getting a pair, but i was turned-off when even m-l told me 93 db was the max i'd get outta them, even if crossed-over to subs at 100hz, which is ackshully higher than i'd like to go. for most music, i'd be ok w/93 db max, but every now-n-again, i like raucous music! :>) that's why i'm considering newform research electrostats - they're more efficient, go louder, and seem to be less sensitive to room-placement than the cls' - they're mono-poles, no sound from the back of 'em. but waf is *really* a problem w/these - i dunno if even *i* will be able to put up w/the way they look! :>) i suggest ewe czech out their www, as well as the reviews (on the r645) on audioreview. more than most of the reviews there, it's impressive what the users ancillary equipment is, & other speakers considered. one guy is using the $17k c-j art preamp, so i don't tink bargain-price was the attraction! these things retail for ~$2250, which ain't bad if they really live up to their claims.