I have had two pellet stoves, one a couple of years ago, and one that I bought recently for my basement. I didn't buy the super expensive kind like the quadrafires or the harmons, I bought el cheapos from Lowes. The one I have now says it will heat 2k sq ft, but that thing better be ran at the highest setting for that to happen. I use the one in my basement now for taking the chill out, not to be read heating the basement.
Both pellet stoves require maintenance, the better versions (harmon/quadrafire)require less maintenance, so you get what you pay for. The pellet stoves at low settings do not put out alot of heat, just check the BTU's on the stoves. I would go with a multifuel stove, something that has some auger system in the burnpot. I bought an el cheapo this year (not multifuel) that I could move into the garage in a couple of years. The newer technologies (switchgrass, garbage, coal pellets) are not standardized yet. I can wait a couple of years to see how this shakes out. Nothing is as warm as a coal or wood stove, with coal putting out the most BTU's.
Corn stoves and pellet stoves can not normally run other types of fuel with out a burnpot change. Mutlifuel stoves can normally run just about anything. Get something with a nice sized hopper, you want to be able to leave it alone as much as possible. My hopper is 120lbs.
My basement is about 2k sq ft, and with the pellet stove on high it will heat it, but I go through about 4 bags at that setting. depending on where you buy, pellets avg about $4.00 a bag/200 a ton.Only buy hardwood pellets. Oil is cheaper for me than 4 bags of pellets a day. But I also like to have a backup.
I won't get into all the other things like rice coal fireplaces, all the required chimney systems, power vents, etc. but they all play a role in what system you can put in and at what pricepoint. You can pick up a good refurbished system (pellet) for well under 2k, or a new el cheapo for about 1500 or less. I paid 1300 for mine (2K sq ft el cheapo) new. In about another 25 days or less Lowes will start clearing out their fireplaces, stoves, and inserts.