No, but I don't think you will be happy with them horizontal. The best setup for MMGs is vertical, and about 16 inches off the floor. Here is a picture of one of mine in some stands I built, sitting next to one of my 3A's.
My first pair of "hifi" speakers were A7-800's in the Valencia cabinet. Got rid of those for EV Sentry 3's. Got rid of the Sentrys (a decision I still regret) for Tympani llla's.
Then tried a number of electrostatics (Quad, Acoustat, Beveridge) before finally settling in on MG3A's (which I still own). While I still occasionally miss the shear power of the old, high efficiency, horn loaded systems of that era, I have come to refer to Magnepans as the loudspeaker that...
Keep it well below any levels where you hear distortion (amplifier clipping). The ribbons are particularly sensitive to that and you obviously don't want to fry them.Most modern receivers have both thermal and current shutdown, so damaging the amp is most likely not an issue.
With all due respect to mr. Gunn, there is nothing that can be done to a 1.6 to even approach the ribbon based high frequency reproduction of a 3 series model... at least not for me.
What you can do to improve them is replacing the internal parts (crossover components and connecting wire), and brace/stiffen the panel and stands.
But frankly, the same money and effort spent on calibration/treatment of the room will result in far greater improvement. Room problems will of...
Note there are two 3As. Tympani llla and MG3A.The single panel MG3a is by far the better speaker. You will need a sub with either for home theater.As for how loud... Hard to say. What is your amp rated at?
I've had all sorts of maggies from the original mgll and tympani llla, to the current 3 series. IMO, anything from the 3 series is a cut above (or can be) the rest. It is the true ribbon that sets them apart... quite possibly the best hf driver I have ever heard.