Which heater to buy?

I am looking for a heater for my greenhouse. It is 12' by 12' by 12'. I was looking at the natural gas heaters since that is what we use to heat our house, oven, and hot water. So it is already made for natural gas. My question is this. Some of the natural gas ones that we found have blue flame which they say is much better because it heats the whole room evenly. The other kind is infrared and heats what is in front of it first. The first one sounds like a much better heater but also costs more. I am at a loss for what to do. And maybe that is not even the way to go. Anyone got any better ideas for me? The other problem is that no one has heaters in stock yet and we have already had some cold nights when it has gone down in the high 40s. Luckily we have a small electric heater that we used to get us through those chilly nights. I would love to keep my greenhouse at at least 65 because of my tropicals and african violets. What should I do?

Jesse

I'll let someone else suggest an appropriate type of heater, but all the greenhouse supply companies have heaters available now if you're OK doing mail order instead of going to the store and buying one on the spot.