Tiny dog: Do I have to stick with small-dog formulas?

She's only about 4.5 pounds, and will be a year old next month.

I had her on Canidae for a while, then switched to Taste of the Wild. She did great on both, but obviously likes the taste of TOTW much better. Unfortunately, neither Canidae nor TOTW say that any of their meats are ethoxyquin-free.

Even though she's doing great on Taste of the Wild, I don't want to keep feeding her the same food all her life (especially if they might contain ethoxyquin). Unfortunately, there's a very slim selection of decent dog foods to get around here - mainly just Canidae and Taste of the Wild.

But, there IS a dusty bag of Wellness that's been sitting on the shelf for the past year. I'd love to feed her Wellness, but there is literally just ONE bag of it at this store (I'm hoping they restock it occasionally, haha). I just remember that it's purple, and it costs twice as much as any of the other stuff. It might have been the Super5 Chicken Mix (since that has a purple bag).

But it looks like Wellness also has a specific formula for a small-breed dog, so I'm not sure if it would be good to feed little Belle one of their generic formulas...

Suggestions?