When you say insert, are you referring to placing a stove into an existing fireplace like this?

What you're considering are heaters. These are airtight woodstoves engineered to heat certain size areas, so in this case bigger is not better. I heat my 1250 sf home here in Vermont with this:

If you put a big honkin' insert in your cabin you'll have every door and window open when it's going just to get the heat out. You'll also need to run a chimney liner to the top because these units have a 6 inch opening and your chimney is much larger. Without the liner the unit will not operate properly and smoke will fill the room.

Is it worth $3000 to $4000?

That's what these inserts are. Airtight woodstoves designed to heat around 1,500 square feet. When you have a fire going and you're within 15 feet of them you get hot.

You can achieve the same effect with a nice set of glass doors and running an outside air source for the existing fireplace at a much lower cost. Get the fire going, shut down the damper, close the doors and you're set.

Quadra fire, Mendota and Valor are good options. Are you going with gas? These units put out a fair amount of heat and are really efficient. You will spend roughly $4k installed for these units. Have you looked at the specs for the units you are interested in?

Good luck.

Hillc, what did you end up getting. I am running into the same problem. I want a wood insert with the biggest viewing area plus something that doesn't eliminate the curve in the stone in the fireplace?

Hillc or gabdoyle what did you end up choosing? I'm looking into same