I have done lots research and asked many questions on the site. A lot really like the Dayton G73! I went with that a few weeks back for my 300 square feet "man cave", but yet to use it. It's all wired up and ready to go, though.
If you only want to heat that area up to 60 degrees or so, you should be fine with the G73 Dayton heater. It is rated for 500 sq feet but it will heat more. just take a little longer to bring temp up.
I am actually going to buy another one to heat my other 1200 square feet up. Since I am only wanting to keep it around 40 degrees (for hot rod cars) during the winter they said it should be fine!