This discussion came up a couple of months ago. Ever since then I have been doing some research.
I started my Wiem on Eukanuba Performance, but I didn't like the results. Then I feed him Purina Pro Plan Large Breed, and his energy, looks, teeth, and stool looked great and I was happy. The only bad thing with Purina Pro Plan, is that he gets chubby really fast if I don't run for a week. I heard the same from other people who use Pro Plan as well.
He kept on getting ear infections, I thought it was just due to swimming and floppy ears. But after doing some research that started from the other tread, I began to think he was having a reaction to the grains in his food.
After 5 weeks of research I started to switch him 2 weeks ago to Taste of the Wild - High Prairie. So far, I think its working. His ear smell MUCH better, his fur is softer, even his 'chubbyness' has seem to calm down.
Gonna be swithcing him over fully next week. I'll let you all know how it goes.