The American Air units are the best on the market. Plus, they have a warranty that is honored and the best customer service possible.
There are other companies selling rebuilt compressor, and I can say, having used them as well, they are vastly INFERIOR to the American Air Suspension products.
Also, if you live in a high moisture area (like I do, in Florida) consider getting the Spider Valve. It will pay for itself by saving your compressor from dying due to moisture build up.