You do not need a lot of power with the Dunlavy's - the Classic 150's are more than adequate. The SC-IVA's have a relatively high sensitivity (~91db) and a relatively stable impedance. Thus, they are conducive to the use of tubes. Indeed, after hearing the Dunlavy's with about a dozen different amps, the best amplifier for use with the SC-IVA's was, without a doubt, the BAT monoblocks (120w/ch).
Dunlavy SC-IVa how best driven
I have been driving my B & W 801s with Northcreeks crossovers with Audio Reasearch Classic 150s upgraded with infinicaps. My preamp is an Audio Reseach Ref 2. Does the IVs require more power to sing? Thus far i've been quite pleased with the performance of my system, but after hearing the IVas driven by an x350 combined with a tube front end, I knew I had to upgrade the speakers.