Just curious. Why Gravity Fed? Siphon feed is less hassle, less chance of spills and you can use a larger jar which means less fills on large models as well as negating the possibility of a spill. Although there is the Badger 260 which gives you the capability for either/or.
I think that the majority here would agree that you should be looking at a Gravity fed double action airbrush, as it's best suited to what you are doing with it.
I am obviously biased, but The H&S airbrushes are pretty versatile, with 0.15, 0.2, 0.4 & 0.6mm needle / nozzle sets available - as you can imagine, the 0.2 & 0.4mm are the ones that you would most often be using, the 0.15mm is suited to superfine work & the 0.6mm can be handy for primer, single colour jobs & clear coats. You also have a variety of cup sizes available for the gravity fed models, as well as a side feed conversion.
We stock the entire Harder & Steenbeck airbrush range, along with accessories & spares. You can see their range of gravity fed brushes here;
http://www.air-craft.net/acatalog/Gravity-Feed-Airbrushes.html