Bob -- the 155 has a single needle/nozzle for everything.. one of the nice things about it. Other brushes that do this that are well made are Omni and some other Badger brushes. Iwata does too but on the CS you have to buy the .5mm needle combo because it comes with a .35 which is a tad small...
I love my 155 and it does wonderful all the way from about a 2" spray down to small lines. It is very easy to clean, breakdown time for major cleaning is a scant minute or so... the Badger 360 which is a tad more expensive (10 dollars more or so I believe) also does gravity fed painting, meaning you can get closer in at a lower air pressure to get even finer detail. The gravity fed cup on the 360 is a tad small so the bottle would be the best bet for large area spraying. And best of all it is the sister brush to the 155 so identical in its spraying traits...
Two things I recommend to get when you order it is needle lube (Regdab needle juice by Badger is avaiable through Dixie Art) and an extra needle. You never know when the needle will get bent on a Sunday night when Michaels or other stores are closed, for only $5 or so it is worthwhile to get one now. Oh yeah the needle juice is only about $5 as well and lasts FOREVER... I've had my bottle about a year and it is still only a fraction from the top.
Needle lube helps keep paint from sticking and especially drying to the needle which is a plague of acrylics especially. This changes the flow of air over the needle and therefore the spray pattern. It also helps keep some of the spattering and spluttering you get with acrylics especially from happening. (It also helps with enamels)
Check out www.dixieart.com and think about ordering from them. excellent service, free shipping on orders over $45.00... the 155 combo with the braided hose and bottles and such is around $59.95 I believe.
Have you thought about your air source? If you already have a construction type compressor you can use that.. if not you can get one at Wal Mart for about $60.00. Then a water trap for about 11.00 and an extra 1/4" male to male connector for about $1.00 and you are set for good! Hobby compressors are quiter but also more expensive. If noise is an issue you can get a reconditioned Thayer and Chandler Air Star on www.badger-airbrush.com for about $99.99 in the garage sale section and it is quiet!!! I use a construction type compressor with a 2 gal tank and am happy with it. The wife says she hardly notices it come on (in the daytime haha... dont use it at night with family in the house, they want to move out after waking to that at 3am)
Good luck to ya and ask more questions if ya have them!