I purchased a gas insert about 4 years ago from heat 'n glo (see link
below). I've been very pleased with it. Nice looking fire, good heat
output, and doesn't use any inside air for combustion. Very efficient.
Heats the immediate room very quickly and if you let it run for a few
hours it will heat a good part of the house. Although keep in mind I
live in CA and it doesn't get that cold outside, and my house is about
2000 sq. ft.
It's a self contained unit. When I moved 2 years ago I took it with me
and installed it in my new fireplace.
My only negative is that the blower is loud when it runs at full
output. Makes it difficult to hear the TV in the same room, so I run
it about half speed (has variable speed control). I also might add I
saved about $400 by ordering it from a dealer in Indiana and having it
shipped. It was about $900 I think. Shop around.