Air compressor help

I highly recommend a larger compressor, 21 gal is about 30 seconds of impacting before the compressor turns on. I also suspect those air numbers are under ideal conditions and are peak numbers, compressors twice as expensive have a hard time keeping up with those numbers. I also recommend an oil-lubed compressor. The oil-lube lasts much longer, is a lot quieter, and can usually supply a higher volume of air for longer periods of time. The bad news is that oil type compressors are more expensive, but worth it. I bought the Sears Professional series 26Gal horizontal, $400. I bought it because it is super quiet and runs on 110V (can be converted to 220V). I use it in an apartment garage and my neigbors cant hear it at all. Check out Lowes and Tractor supply too, they have some huge 60gal oil comps for around $400.