The reality is that the MA5200 is designed for an 8 ohm nominal load, not 4. Given how well make Mc is, it won't fail, but it is safe to predict that it won't sound its best either.Well said. This is exactly why I stayed away from this amp as I have 4 Ohm nominal speakers. If it was stable into a 4 Ohm load, surely McIntosh would have published the specs. They did not and even went so far as to stamp 8 Ohms only on the back panel by the speaker terminals.
I am willing to bet if McIntosh was contacted, they would not provide a 4 Ohm rating. If they did, then again, why not say so out of the gate like they do for their higher level products. As for the stereo mags review that was sited, well IMO you have to take those with a grain of salt.
Again, I strongly considered this amp and auditioned it with a pair of Sonus Faber Cremonas, a 4 Ohm speaker. And while the MA5200 did drive them, the Marantz PM15S2 (90 wpc into 8 & 140 wpc into 4) did a much better job. So much so that this is the amp I went with to drive my VA's and have no regrets. I would suggest to anyone with 4 Ohm speakers to be leery of this particular Mac product.