What are you using now? I have the HP-C not the new + model, and just love it. It's the best airbrush I've ever owned. A real work of art. I bought a preset handle for it, a must in my opion. Makes consistent fine lines easy. I think the C+ comes with this, and a teflon needle packing, so you can spray laquers with it.
Save yourself the money and go with the HP-C+. You can buy two of the C+s for the price of one micron. The micron is made for spraying extremely thin illustration paint. Its nozzle is only .18 mm. Not good for spraying acrylics and enamel. And don't worry, the C+ will be able to spray any kind of fine line needed to model. You just have to setup the airbrush properly.
Also if you live in the USA. Check out Dixie Art and Airbrush online. They have the best prices, and dont charge you shipping. I get all my airbrush stuff from them and they are simple the best. I placed an order online for a new compressor, the Silent 20A, and they called me back an hour later and said they didn't have it in stock and offered me 30-TC, (which cost 75 dollars more), for the same price. To make a long story short I ended up with a Silent Aire DR-300, it cost me an extra 25 more dollars, but that compressor rocks, super quit.