Beneful, or pretty much any grocery store brand of dog food for that matter is not a very nutritious choice. I had Nick on it at one point, too. I didn't have any problems but I started learning more and more about what is in commercial dog foods and it is TOTALLY gross!!
If you have a PetCo near you, that would probably be the easiest way to see some examples of premium dog foods. They carry brands such as Natural Balance, Wellness and Solid Gold - all of which don't use fillers or by-products.
There are some good posts on here that talk about the yukky stuff in kibble. A website I love is
www.dogfoodanalysis.com. This rates different brands of dog foods and tells you why it scored what it did. When I wanted a higher quality food for Nick, I started emailing several top rated brands and asking for samples. Most are pretty good about letting you try their product before you have to buy.
Some good brands you might want to check out are Innova, Orijen, Wellness, Solid Gold, Nature's Variety, Halo, Taste of the Wild. Most of these companies have kibble specifically designed for small breeds.
Good luck!