Now! and Go! are wonderful foods, IMO. I really like Petcurean Pet Foods and completely trust them. The kibbles are also smaller, so if you have a Yorkie who likes smaller kibbles, it's a great choice
We've always had great luck with Go! Endurance [grain-free]. The only reason I stopped is because my picky boy decides to stop eating smaller kibbles usually... he likes bigger ones to crunch.