It's all about technique fellas. I have $500 Digital pressure gauge Sata's and A few Devilbiss guns, and I even have separate guns just for primer, white paint, and clear coat.
I could make a really nice looking paint job with a $50 gun though. It's all about experience, setup, temperature, technique and setup. If you're spraying a car, i would at a minimum, have a 10CFM compressor. Dust and moisture are your worst enemies. Filters, filters and more filters.
My personal setup is a primary filter that takes out water with a disposable dessicant that you you have to change when the little balls turn blue (means that they can no longer hold moisture) and then I also use disposable inline filters at the gun. Typical cap pressure with a 1.4mm basecoat gun tip should be around 10-11psi, with inlet pressure regulated to 35psi (not all guns can tell you this, my sata digital display shows both cap and inlet pressure), with clearcoat, I usually use a 1.2 or 1.3mm tip, and I bump the pressure up to 40 psi for better atomization (sorry for the imperial numbers here, we don't use kpa) Primer gun, typically a 1.6mm tip, sometimes a 1.8 if it's a really high build primer.