I had a single stage 60 gal and upgraded to an 80 gal 2 stage. It is made by a local outfit here called C'Aire and is industrial quality. For spraying, I use a turbine driven HVLP but the air sanders can really work the compressor. It has enough capacity to keep up when I use the 6" ROS full on as it will catch up and stop eventually, but it does run a long time. Since heat is the enemy, I point a shop fan at it when I run it hard to help cool it more. So the question is what do you really need? Someone mentioned needing a portable one and that is for sure, but those can be fairly small, and you probably have it covered with your 20gal. If you have the space and power for a large fixed unit, it can allow you to run sprayers and high draw air tools like sanders and blasters that you could not do very well otherwise.
Ingersoll used to be a good brand but it sounds like they have become trash in the past few years. I have seen several people complaining about defects in new IR compressors and very poor response from the mfger so I would avoid them. Most of the cheaper brands you will find in Fleet Farm, etc are going to be lower quality which may or may not be enough for what you need. If you rarely run them hard, that may be fine. If you run them hard all the time, then they will prob not last. But if you are going to buy a cheaper/less durable one, don't spend extra for a name like IR that has lost their way. Quincy is a known good brand but I have also heard they have a cheaper line of imports now. Atlas Copco too is higher end. All depends on your needs and wallet.
