There are many manufacturers out there. Do searches using different search criteria and also look at the images on Google, if you use that for a search engine. You will come up with many options from which you can make a better informed choice.

Alex, It all depends on what you are trying to do with the greenhouse, what you want out of it, where you are at, etc. I would consider the greenhouses you are looking at more like a season extender. For example, If you are in an extremely cold climate and you want to heat this particular greenhouse to grow tomatoes in the winter it will cost you a lot to heat. This is because of the type of covering it has. If you are trying to overwinter some plants and just need to keep the frost off them, or to heat it slightly, this would be a fine choice. So, I think the first thing you should determine is how you are going to use the greenhouse. What are you going to use it for? How long do you expect it to last? How high will you need to keep the temperature? Then, make a choice. There is a formula for calculating the size heater you need for a greenhouse. The parts of the formula include the size of the greenhouse, the temperature difference between outside and inside the greenhouse and the R value (insulation factor) of the material covering the greenhouse.

What's your objective? How big? How long do you expect it to last? What's your maximum budget?

Your original question was the equivalent of saying: I'd like to buy a car...what do you suggest?