I agree with Les, for painting model airplanes, particularly if you're doing flat finishes, I love my Sata's, but I have the benefit of purchasing them for work use and personal is just a bonus
Anyway, how many CFM's will your compressor put out? My compressor (which I need to upgrade soon) is not an expensive one, it's a home depot model, I paid $699 Canadian for it, it's probably cheaper in the US, it's a Husky model, and it puts out 11.8 CFM at 40psi which is more than enough for the RP (or most full size guns). It is also 100% duty cycle which is good because when I'm painting a car it runs almost non stop but keeps up fine, the downside to running nonstop for 30 minutes at a time is it's really hard to keep moisture to a minimum.