It might be interesting to note that Rick Rubin produced that album for Cash. Rick Rubin did Slayer's "South of Heaven." So, if you like the dark sound of Cash in that instance, that's because it has the hand of heavy metal in it. Like it or not.
Rick Rubin can go from Slayer (Reign In Blood was what it was I think because of him) to Shakira..to the Beastie Boys. Actually Reign In Blood and the first Beastie Boys album were made around the same time..Kerry King even did some guitar work on that album.
And it was the remake of Dawn Of The Dead that had that Cash song in the beginning...pretty fitting I think.
But back on topic...
My take on backpacks is buy quality and buy what you like. That doesn't nessesarily mean "expensive".
I see people every so often walking around with ratty old Jansport (or similar) packs that seem to be more dirt than fabric..but they hold up. These people have probably walked the earth twice over and their packs have been crushed under bus seats, thrown in snow, backs of pickups, through scrub brush, in the rain, sun, stuffed with clothes and junk etc.. They didn't have $300 to spend on a "great" pack and probably grabbed them out of a pile of trash, but it's more of a "BOB" then most of us will ever use.
I was thinking of getting one myself and trying it out..the old two pocket, leather bottomed standard backpack.
EDIT:
A simple pack like this might make you re-think some of the "stuff" you've accumulated to put in it. First aid kit, canteen, energy bars, map, small radio and one or two things..I find the more pockets and pouches I have on a pack, the more I want to fill them up.