I did a heap of research on what you need to use to get a good even coating of paint.

For most spray guns available, you will need to have a minimum of 15cfm compressor, pushing about 115psi out. The tank size is not critical, but it allows your compressor time to relax between pumps. A bigger tank is always better, but not critical.

Reguardless weather you have a gravity or a suction type, you need these pressures and volumes to get antything to work well.

I spoke at length to my local panel beater about this. His suggestion was to not bother with the high pressure, low volume stuff you are talking about and get the biggest compressor that you can afford.

I run a 17 cfm compressor, which is the biggest that you can get on single phase and I use a gravity gun or top pot, and have had no worries with it so far.

basically, my opinoion, get a 17 cfm compressor, 40l tank minimum, and go and speak to a trusted panel beater for some specific advice.

hope that helps.