i install automotive electronics and build custom fabrications. I use a BOSTICH brand bradnailer/stapler and it has preformed flawlessly after hundreds of uses. For crown molding just about any brand will suffice, however I am not sure exactly what staple or nail length you would need . . . depends on how thick your molding is and what your tacking it into . . . probably a unit that is capeable of at least an inch and a half . . . craftsman has quality air tools at an affordable price. here is a link to a stapler and nailer combo, which also comes with staples and nails which may for for your application . .
bostich and portercable are more well known brand amoung air tools . . . but this craftsman unit has a nice price.
Sears.com