Welcome to the Forum.
Paasche H Set comes in at the lower end of your price range. Although single action external mix unit, it can paint a pretty narrow line. Quite sufficient I think for 1/48 A/C. The Set comes with three tips, although unless you need a wide enough pattern to varnish a table, you can usually stay with the small tip. It's rugged, easy to ease, and clean up. I use mine for acrylic painting, clear coats, and with the large tip for varnishing.
I also have Badger 200 NH, a single action version of their Anthem 155. A darned fine brush which I use for all my enamel painting. I would recommend it but the way pricing usually seems to fall out, I would probably recommend either the Paasche H Set for low end pricing, or a double action Badger such as the 100 for higher end pricing.
A lot of people do like Azteks, but I have been down on them ever since mine died for no apparent reason. I followed all the cleaning and care instruction to the letter, and it stopped working after painting only a few models. They did fix the thing per warranty, but during the three week turnaround, I bought the Badger and have never looked back.
Whichever air-brush you look to get, I recommend DixieArt.com. They have really good prices, before Katrina they were always quite reliable and it looks as though they're getting on their feet again, and could probably use all the support they can get.
Andy