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.