I feed my boys Fromm's "Four-Star Nutritionals." (they receive a 5-star review on most sites
). All of their flavors have very small kibble, smaller than Orijen or the regular Natural Balance.
The other food I use is Go! Endurance. I believe all of the Go! and Now! products from Petcurean have small kibble and it is all tasty stuff.
My boys didn't do well on Orijen, Acana, or Merrick Before Grain.