Man, you got Gunze Sangyo and Tamiya airbrush all around you... Tamiya's HG double action airbrush works really well with enamel or acrylic paints and comes with a preset handle. Same applies to their HG-SuperFine airbrush, though it has a smaller cup size and a finer nozzle/needle assembly. Those two together pretty much got you covered for most of the types of models. Similarly Gunze's Mr. Airbrush series comes with for example Procon boy which has two nice double action gravity feed airbrushes to cover all your needs. Gunze also makes pretty nice quality aircompressors with regulator/moisture trap all built in. For a little more money, Anest Iwata's HP-BP, CP, BH, CH can be considered to cover general coverage and details.
You got to get an airbrush to suit your needs. They differ in nozzle/needle sizes for different types of paints and different spray area coverage that they are suited for. To change the airpressure you'd be looking at a compressor with a pressure regulator. The Iwata Hi-Line series (HP-BH, CH) does have those fine tuning valves for airpressure built into the airbrush body but they don't change by a lot.
An exchangeable set of different sized needle/nozzel for the same airbrush does help save some money, so if you don't want to spend that much, that'd be the way to go. Iwata does have their Eclipse series, for example the HP-CS which comes with a fine needle/nozzle set at 0.35mm but also offers a 0.5mm larger size needle/nozzle set as an option to increase the coverage to use it for model car bodies and all.
So... what type of models do you build?
*where is musiccity's airbrush guide when you need it... somebody help with the link*