First,sushi, on MCACC(Multi Channel ACoustic Calibration),although I haven't tried it, my impression is that the great majority of reports from owners is highly favorable. It would seem that if even a partial correction of response irregularities caused by the listening room and/or speakers can be achieved with so little bother, that it's a worthwhile addition to a receiver. It should be noted that Pioneer announced at last month's CES that 3 of their new line of lower cost receivers(out in March)would have MCACC, including a microphone for automatic operation on the 912( 6 X 110 watts; probably $300-$350 street price).
On the 4ohm question, I suppose that we've read the same reports and they're so conflicting that I don't know what to make of them. The technical reason given for the rumored "fix" a couple weeks ago made no sense to me. I'd be inclined to give it a try. In roughly the same price range the Denon 3803 and Sony DA4ES would also be fine choices(wonder about the loud fan reports on the HK525).
