With the size of your fireplace opening, you probably won`t be able to get anything with a larger firebox. Hence your burn times will not exceed 6 hours max. The vista will be plenty of heat and the blower shuts off automatically when the unit is no longer producing usefull heat.

It is too bad you can`t get something with a larger firebox (at least 2.0 cu.ft),because you can always build a smaller fire in the larger firebox, but you can`t build a bigger fire in a small firebox. Heat-wise the vista will serve you well, but if you want continious heat then you will have to get up in the middle of the night to feed it.

First of all I would be more concerned about safety than area heated At the very least any insert would have to be listed for installation in a prefab fireplace Second how would you sleep at night knowing that much heat is only inches away from combustiable framing Another point there were no UL listings for t your original heatalator you would be installing an insert into an unlisted surround Personally as an inspector I would never issue a permit for the installation On the other hand some heatalators were built into proper masonry fireplaces From here I can't examine yours to confirm its construction My question would be before I do anything how safe is my existing setup? Noy fretting over models or manufactures Another thought what precautions have you taken concerning freezing of your pipes? If you successfully heat with wood will your pipes freeze? Remember they circulated water, now they sit stagnant possibly exposed to freezing. You would not be the first one to discover that situation when its too late.
http://www.hearthtalk.com/ You might want to post you concerns here

Sonny and elkimmeg ~ Thank you both for your input:

"Heat-wise the vista will serve you well, but if you want continious heat then you will have to get up in the middle of the night to feed it."
Point well taken. At that point, the oil burner should kick on until we're up and about in the morning. Middle of the night feedings are reserved only for children, and ours is grown ;o)

"At the very least any insert would have to be listed for installation in a prefab fireplace."
The Vista is approved for installation in an existing zero-clearance fireplace.

"Second how would you sleep at night knowing that much heat is only inches away from combustiable framing."
We are removing the wood mantle, replacing it with a bluestone mantel. The closet framing, wall or combustible is 4 feet away from the fireplace/insert.

"On the other hand some heatalators were built into proper masonry fireplaces."
Ours is built into a proper masonry fireplace.

"My question would be before I do anything how safe is my existing setup?"
Inspection done and anything that needs to be modified or corrected is being done.

"Another thought what precautions have you taken concerning freezing of your pipes?"
We are using our oil burner for heat, as well. Since we use our water (hot and cold) on a daily basis the water running through the pipes will never be "stagnant". We also have a propane hot water heater, which is located in the garage/basement. This throws off a certain amount of heat which is close to the cold water pipes. The hot water pipes run from the propane hot water heater. In any event, we will not be as remiss as to let our pipes freeze. We're planning on utilizing both sources of heat (insert and oil), and hopefully it will accomplish our goal of reducing our oil costs dramatically.

There two approaches to saving heating cost an axillary heater wood stove. and preventing heat losses in you existing home All exposed hot water pipes in the basement For heating and hot water should be insulated to R-5.0 or greater. This would prevent freezing to an extent and reduce transmission loses. It also saves water running the tap till the water is warm enough that time would be reduced less water down the drain.
Set back thermostats Studies prove that setbacks on forced hot water systems are effective up to a 6 degree temperature swing Beyond that it uses too much fuel to restore the desired temperatures for any savings Studies also indicate a permanent lower thermostat setting becomes even more effective than the set backs.
Add insulation to the attic ceiling area Seal the sill plate and foundation contact weatherstrip exterior doors Add insulation to the cellar floor cavity. That area is subject to a 15% heat loss to your living space R19 or greater can reduce those losses Draft insulation behind all external electrical outlets. Reduce your heat losses saves money and holds heat in

elkimmeg ~ thank you for your insight, expertise, and suggestions. We already have done everything on your "hit list", except insulating around the water pipes, which we will do. Our hot water heater is less than 2 years old and already set back, attic is well insulated, sill plates on exterior doors are done/weatherstripped, and the cellar/garage floor well insulated. Our house went through a major renovation/reconstruction about 10 years ago. At that time, we put in all new windows and doors, stripped the interior walls to the studs, re-insulated and sheetrocked, exterior insulation and siding, new garage door, everything that could be insulated and sealed (except the water lines in the basement/garage...which we'll do now).

Good Job, that being the case, no matter what wood stove you purchase It should heat well