Feed stores are your best bet
Most of them seem to carry the good quality brands.
Oh - and the store locators on the manufacturer websites tell you about stores that carry it - it's not internet sales (though some may do that as well).
Here's the list you're looking for: http://boxerworld.com/forums/showthread.php?t=66384
And the selection criteria used by the WDJ (which is similar to that at www.boxerworld.com/feeding
) is posted further down the same thread.
Not every food on that list is equal, of course, but they're all good quality and any one of them would be a pretty good choice.
If I had to list the "best" of them, that list would include Timberwolf Organics, Canidae, Chicken Soup, Innova (especially EVO if your dog is an adult, but not for a pup), Fromms Four Star, Artemis (especially the fresh mix), Wellness, and some formulas of Merrick.