If the Cirrus can be biamped try the KT88 amps on the HF section and a decent SS amp on the LF inputs.......I have used such a setup for a long time and it's a true marvel mated with high rez transducers (ribbons/planar) with the excellent ability of a class A SS amp controling the bass transducers with an iron grip.
Tubes and SS can happily coincide as long as one is careful to match amps for the freq range being used and to take special care in setting levels for the various driver sets. The only caveat to tube amps is the impedance they might see from a driver..if your driver(s) dip well below 4 ohms within it's operating range a tube amp may not be the best answer. Ribbons can have a funky impedance curve.
Edited by Pricklely Peete - 6/3/11 at 4:20pm