@tomcarr I’ve never seen an impedance curve for the 801 S2, but I checked the user manual specs and found that while they are rated at ‘Nominal 8 Ohms’ in parantheses immediately following it reads “not falling below 4 Ohms.” I expect the drooping impedance would most likely occur in the lower frequencies. I think I’ll try the MC252 taps for the low frequencies over from 8 to 4 Ohms.
I also checked the specs on the MC252. Since it has autoformers, it can deliver max power however you hook it up: 250 Watts in stereo and 500 Watts in mono continuous sine wave with up to peaks of 50 Amps to each speaker. We’re I to go back to using both MC252s on the B&Ws I could run them either bridged or parallel into 4 Ohms. The parallel configuration would deliver the most current, I would think. One day I may try it, but after lugging that 96 lb. beast upstairs yesterday, it’s not going back down for a while. It seems perfectly suited to drive the XRT20s.
@erik_squires Point taken on using identical amps as monoblocks. To be honest I was a bit intimidated at the prospect, I was afraid I might blow something up. But there is plenty of protection built into the McIntosh amps. I may try to source an MC2255 for the XRT20s and move the MC252 back downstairs for the B&Ws, or possibly bring the 65 lb. Rogue upstairs for the XRT20s, although the XRT20s could bring the Rogue 100 into clipping, and does NOT have the protection the McIntosh units provide. I think my current configuration makes the best use of the power I have available.