If you are thinking of an Iwata think no more. They are the best brushes out their at this point. All you need to nail down is whether or not you want to go wtih double action, single action, siphon feed or gravity feed.
I personnally use a Badger 175 Crescendo double action siphon feed. It works great, comes with three different tips and has a metal body and to me, is easy to clean.
I've heard single actions are much easier to clean since it doesn't go through as much of the brush.
I have found that most people who pick up a brush for the first time usually fall in love with that. Meaning if you bought a double action you'll learn it much better therefore making a single action a little tougher to work with or vice versa.
IF you need more info I would be more than happy to help. I plan on picking up an Iwata this spring for flame jobs and special work. My Badger 175 is my workhorse.
If you are familiar with Mike Lavelle, he is the creator of the real flame phenom right now. He uses an Iwata.
I would stay away from the testors stuff if you already know how to air-brush. I usually recommend that for first timers to get their feet wet and learn. This way they don't spend too much money right off the bat and can get an idea of what is involved before they drop some real coin on a quality air-brush.
I would also recommend a quality compressor. You can pick up a decent C/H compressor from the mart store. Make sure it has a pressure regulator and water trap. These two things are vital for your work. If you plan on working late at night while the family is sleeping I would recommend a silent/aire or Iwata hobby compressor. These are auto shutoff, have no air(holding)tank, come with all the items you'll need (regualtor/trap) and are super quiet. The only problem is these are expensive. What you are paying for is the silence.
To get some good pricing hit
www.bearair.com
They have some great info on their site that will help tremendously with your decision.
Good Luck!
Chris