I'd get rid of the 450's and go with a pair of 444's, 480's or 485's. Higher working pressure, higher pressure at 100% duty cycle, and lower amperage. Here's a link to Viair's comparison chart.
Also, you asked about compressors, what are you running now? I have 2 5 gallon tanks and 2 Viair 444's. Fill time is quick from 145-175 and they have 100% duty cycle up to 200 psi, I don't think you will need 4.