Mont, maybe we need start at the bottom. 2 stage means air comes in at atmosphere. pressure and is pumped up to say 50psi. the in goes into the 2stage at 50 psi. and comes out at 150 psi. Its slower building vol. but high on pressure. The single stage 2 cyl. will build air faster, but not as high pressure. Now the extra tank is goin give you more vol. its goin to take longer to fill the tanks, but when it does, it'll take longer for the pressure to run down,cause there's more to run down. As for a compressor, see how many cfm of air your tools use. If the highest is say 9cfm, I get a compressor that would product at-lest 7cfm. That way if you let the tank fill (150psi) and you start using the tool, when the pressure drops to the low level switch (100psi) the pump comes on and starts rebuilding the pressure as you using it. making 7 cf a minute, and using 9cf a min. it'll take longer to drop down. Hopefully you ready to stop for something and the compressor keeps building.