Hmm... My rec would be a Paasche VL or similar if you're just going to use it for base layers and overall color (or masked areas). An Iwata is quite a nice airbrush, a once in a lifetime solution. I use an Iwata HP-C for about 80% of my airbrushing, and an HP-SB for detail work. The C will get as tight, but I have more confidence in the SB for tight stuff. You can generally find these for much less than original prices, as the Iwata Custom series has supplanted them as the company's top range.
I've heard very good things about the Azteks, but I don't know how long they last and what kind of maintenance they require... I've had my C and SB for over 10 years, with only occasional needle replacements and only one nozzle replacement each. The Paasches are really long-lived as well.
Equally important to consider is your air source. I have a silent oil compressor (Ralph McQ's old one) and it's a gem. You can look into hobby compressors as well as compressed air tanks (but be careful who re-charges the tank for you... they need to be told not to use certain lubricants as they will contaminate the line)... AND you must get a good moisture trap and regulator as well, if they aren't built into your compressor... this will take you out of the 150 (total) range I'm afraid.