I got an email notification about Lars' reply. I'm happy to give an update.
We ended up going with the Lennox Montecito (55,000 BTU, 2 cubic feet). The house is 1550 square feet, and the ceiling in front of the fireplace is approximately 14 feet high. We have a reversible fan directly in front of the fireplace on a 2 foot downrod. We've been in the house for a little over a year, so we've only had 1 winter worth of fireplace use so far. Over the winter, we had fires an average of probably 2 or 3 nights a week, and some weekends.
The wood I had last winter wasn't the best, so it was often a struggle just to get a good fire started at all. Because of this, I didn't really experiment much with turning the blower and ceiling fan off to simulate a power outage. After spending an hour or two to get a fire started after a long day of work, I wasn't in the mood to do experiments, and definitely wanted to get as much heat out of my effort as possible.
This coming winter should be better. I cut and split the wood much earlier in the year, so it should be much better seasoned than last winter. I have a lot more wood, it's all already split, and since it won't be green, the fires should be a lot easier to get started and maintain, so I intend to experiment with leaving the blower and ceiling fan off.
However, I can report on how it worked with the blower and ceiling fan on, using mostly green wood. Once the fire has had some time to really get going, the Lennox Montecito had no problem heating our entire house, even on very cold nights. The blower is on a dimmer switch (which also has an off setting). We'd usually run it on high in the beginning (right after the thermostat kicked it on) as it was heating up, and then we'd switch it down to medium. On a 30F night, with the regular oil heat thermostat set to 60F, within maybe 3 or 4 hours of starting the fire, the living room would usually be around 75F and the bedrooms would be around 67F, which is just about perfect. If we planned on spending more time in the living room and didn't want to be sweated out, the living room temperature could easily be lowered by lowering or disabling the blower, adjusting the air combustion control, or by keeping less wood in the firebox. The ceiling fan on reverse seemed very useful for distributing the heat around the house (thanks, begreen). The blower isn't too loud, but is definitely noticeable on high, and barely noticeable on medium. It takes a while for the fireplace to get hot enough for its thermostat to kick the blower on, and there's no way to force it on manually.
The fires required a lot of maintenance and would only burn unattended for about 4 hours. I'd fill the firebox with as much wood as I could fit at around midnight right before I went to bed, I'd set the air combustion control to medium, and the fire would be completely out by 7AM when I woke up. The fireplace would still be warm to the touch, but cool enough that the fireplace's thermostat turned the blower off (usually at around 4 or 5AM, I think). Because of this, I'd have to set the house's oil heat thermostat to around 65F before we went to bed, otherwise we'd wake up freezing. Occasionally there would be some visible embers glowing in the soot (sometimes even for days after). I'm not sure if those would be enough to start a new fire. I didn't try it because I'd be heading off to work, so there was no point in heating an empty house when I knew the fire would be out by the time I got home 9 or 10 hours later. I'm hoping that I can get better burn times this coming winter (they advertise up to 8 hours) by closing the air combustion control more. I didn't go much below medium last winter because I was using green wood, and I was nervous about creosote build-up. With better seasoned wood, that will be less of a concern, so I can try closing the air combustion control all the way before I go to bed to see if I can increase burn times.
I hope this was helpful. Let me know if you have any other questions and I'll be happy to try to answer them. Maybe if I remember, I'll try to post an update this coming winter after I experiment with how it works with the blower and ceiling fan off.