I used a 60 gallon, 10.2 SCFM Husky Pro (single stage upright head, average hardware store model) until one of the reed valves gave up this summer, but within about a month I moved into my new shop which had an old IR dinosaur with a Model 30 head (V-twin compound, cooler between cylinders, etc.) and 60 gal. tank that still worked, more or less. So I plumbed the Husky Pro inline with the Ingersoll and just used it as an extra tank, but the old compressor struggles to keep up with any extended use of a die grinder, etc. so I got ahold of an Ingersoll head that'll fit the Husky (buddy has the scrap contract for the IR factory in town) and just got it bolted on last night. Gotta get a belt for it and then I'll have 120 gal. of air and at least 18 CFM judging by the dinosaur's output compared to the Husky's.
With that combo I'll stage the old compressor to kick in second to keep it in one piece longer, and shouldn't have to worry about letting up at all with a die grinder, DA sander, etc.