I agree on the double action brush idea... I know the single actions are great and can do the job, but the double action will prove to be more versatile over time when you get more used to airbrushing.
You would want to buy something of decent quality and still remain within your budget. The badgers you listed, along with the Badger 155 (which I own one of) are great brushes. The Iwata HP-CR is a great brush and I own one of those too..it is capable of some great fine detail! Actually if you got the Badger 100LG with the medium head and needle, later if you decided to try your hand at German squiggle camo or such, it would be a simple matter of buying the fine tip and needle for it.... a fairly versatile setup! Plus with it being gravity fed I think it will be able to get into some tighter detail for you even with the med head.
I also recommend getting a bottle of airbrush lube with it. It is a oil like substance (actually I believe it is made with glycerin) that you coat your needle lightly with to prevent paint from building up on it and disrupting the airflow over it... it really makes a difference. It's about $5.00 for a bottle of it and it lasts for years... it goes by Regdab needle juice, or Medea Super lube.
And as one last item to put on the order form when you get it, an extra needle is handy to have too in case you bend yours late one Sunday night and have to wait to get another one till the next week... again, about $6 to $7 for an extra one...
I've got all but one of my airbrushes from www.dixieart.com and had great results... they also have free shipping on any order over $45.00... can't beat free! They have great customer service too...