I live in a house of a similar size. We have a 3 cu feet Travis Hybrid Large Flush Insert. We've been burning it almost non-stop since October.
We are only "medium" happy with the heating ability.
1. The fireplace is in a two story family room. Even with the ceiling fan on high, much of the heat is lost to the upstairs. Even during this past cold winter (Penna), we could just about turn off the heat in most of the upstairs (4 bedrooms, 3 baths) if we left the doors open. It is amazing that when you walk halfway up the stairs in our family room, the temp seems to go up about 5 degrees.
2. These inserts are A LOT OF WORK
Like is said, many of us find the wood cutting and fire tending a pleasure. I'm lucky to live on a country property with an endless supply of primo wood. It's my hobby, exercise and sanity keeper to be out cutting, hauling and stacking.
3. Then there is the tending. Insert needs to be fed about every 6 hours. In the am, it's hardly putting out any heat, but starts up w/o new lighting, just a few small pieces of wood and crack the door, starts right up. The ashes need to be cleaned out every 5 days or so when going full tilt. Also, we are lucky to be able to stack the wood up right next to the fireplace, but there is never ending sweeping the hearth area and then vacuuming when the wood goes down, taking wood in, and just in general. But I don't find it a chore.
4. The fan is noisy. It's completely adjustable, and works fine at half speed, but I would think the output is down at half speed, but it's hard to listen to TV at full speed.
5. Be careful that you have enough hearth. Our opening is raised from the floor about 16 inches with a stone in front of opening that's about 8-10" wide. But even with about 30" between opening and rug we have had some ashes pit on the rug, when tending the fire. Also, as the ash builds up, it tends to overflow onto the hearth if a log falls forward inside.
6. If you have to buy your wood, I don't think an insert is worth it, but if you can get it for free, have a good back and enjoy all the work, and enjoy a fire, then go ahead.
7. Before we installed the insert, we were burning almost every evening anyway. I have no regrets whatsoever about putting this insert in. Although realize by the time you get done paying for installation, chimney liner and etc.'s, the total price could be 2.5 x the insert. Be careful if you think you could do it by yourself, maybe you can, but you don't want to take any chance of a fire in that expensive house with an amateur installation job.