Most find it more beneficial to put a rear venting freestanding stove in front of the fireplace. You might also look into a wood furnace and hooking into your duct work with that much sq footage.
Another larger insert is the: Buck Stove model 91
I started looking into wood burning furnace add-ons. I'm located in Connecticut, and other than big box stores or online, I can't even find a place that sells and installs them.
After doing some more research on them, they sound promising in terms of being able to heat a large area. Just not sure if they are available anymore around here.