I just recently changed from B&W 802's, which I owned for a very long time. My main criticisms of that speaker seem to be the same as yours, a little harsh on top, and not the most natural mids available. I tried many speakers ranging from Audio Physic, Meadowlark, B&W Nautilus, ProAc, Vandersteen, System Audio, Silverline, Soliloquy and others. What I ultimately decided to buy were British monitors, specifically Spendor SP 1/2's. I purchased the Spendors over the Harbeth models because I own push-pull tube equipment, which matches the Spendors extremely well. If I were the owner of high-powered quality SS gear like you, I would not consider my search complete without at least trying a pair of Harbeth speakers. Prices new range from about $ 7000 for Monitor 40 to a little less than 3k for Compact 7's. See Bob Neills reviews on enjoythemusic.com as a starting point. He talks about a similiarly sized room to yours, with similiar listening tastes. I believe that you could get a money back guarantee for an in home audition if there are no dealers in your area. YMMV, of course, but if naturalness of timbre is important to you, at least read the reviews.
Mike
Mike