Modern Audio is indeed the distributor in the US. I had occasion to call there a few weeks ago, and during our brief conversation my primary sense of things was that the guy wanted to get off the phone as quickly as possible.
In conversation with a well-established high-street dealer in the greater DC/Maryland area (who does not sell Proacs), he stated that he could not think of a less pro-active distributor than Modern Audio. I have no opinion on the matter, merely report this opinion. As far as I can tell they do not distribute any other brands.
As far as I remember, Proac took a series misstep with the Future line, and while they have now come back to the tried and true, their current prices when translated into US$ must make them somewhat difficult to sell, given the fierce competition in the loudspeaker market. I know that I looked at them seriously recently and passed.