check out this thread:
http://www.s10forum.com/forum/showthread.php?t=211676&page=2&pp=30
DJDAudio had been doing all kinds of tests, they're not faster than 2 450s, but close:
"(1) AZ comp 110-145 is 3 min 14 sec on a 12 gal, 35amps
(2) viair 450C's 110-145 2 min 40 sec on a 12 gal, 40amps"
roughly an extra 30 seconds or so (at those pressures/size of tank) so they're awesome. Adding 1 450 is probably more practical since it's temporary anyway.