Is the excessive wear on the inside or the outside of the tire. If it is on the inside part of the tire, there could be some excessive sag in the front end, This could be encountered with the additional weight of the plow.
You could install some rubber spring spacers or buy an optional front preloader kit for that model of machine which could help with the sag. You could also get a heavy duty set of front springs.
Finally, as far as Tires go, Maxxis Bighorns will get the most votes here on PRC. They are a great all around tire, that peform very well in a variety of terrain.