I like my Nimrod backpack system - quiet material, rugged zippers, all the nice attachments like bino bag, padded spotting scope holder, ammo bag, rifle scabbard, detachable fanny pack, etc.
Nimrod makes packs for firefighters / SAR personnel, too, which is where I got to know them. Here are some testimonials:
http://www.nimrodpacks.com/testimonials.htmlPrices are generally $350-400, but I got mine for nearly nothing at an Elk Foundation auction.
Good luck!
P.S. Nimrod is made in America!