As a former McCormack amp owner (0.5 deluxe), I'd say you should think about mating it with a tube pre-amp. I first tried a passive and then an active SS pre-amp and felt the midrange was just too lean. Trying it with my friend's Quicksilver preamp showed me what I was missing in the midrange and I began seeking out tube preamps. Of all the preamps I tried, I liked the Audible Illusions 3 the best with the McCormack. YMMV of course, but I think tube preamp will get you the sound you want.
