Hi Jae, When I first started looking at incubators, I only wanted a small one as I was only going to hatch a few each year... now I have 4 with a total capacity of 128 eggs!
The best value (fully auto) incubator on the market at the moment is the RCOM King Suro sold by P and T Poultry. You can buy them for 136 pounds from their ebay shop, and delivery is within a couple of days (only took mine three business days to France!) They are a little more expensive in their normal online shop, but still cheaper than many other incubator suppliers.
P and T are also the only official suppliers of RCOM incubators in the UK, and are able to back up the official 2 year warranty.
Another plus, is that they are extremely knowledgable, and will respond to questions by email in less than half a day! (I am unable to phone thier line as it is an 0844 number)
I have now bought three inubators from them, and wouldn't hesitate to recommend them to anyone.
The Suro incubator will has a capacity of 20 hen eggs, but you can also incubate quail, duck, goose eggs etc (believe me when I say hathcing 7 or 8 will NEVER be enough!). It auto turns the eggs by rocking on a cradle. it is forced air, so that the temperature is even throughout the egg compartment; there is computer controlled humidity regulation so you don't have to worry about the air being too wet or dry, and you only have to increase the humidity in the last three days.
Plus, the top of the incubator is transparent - which is very important for when you want to watch your eggies hatch!
However, everyone has thier own opinion on which is the better incubator!
My favourite is my RCOM 20, but that maybe because I am more famiiar with it as I have had it the longest!