There's a lot of controversy out on whether or not the super-high protein in most grain-free dogs is good for them or not (especially when its just a companion dog, not a high-energy working dog); like you said some studies show it can cause liver problems. It's mentioned in a lot of the dogfoodanalysis.com reviews for some of the common grain-free brands.
Evo for example is prolly rated as one of the best foods but has I think over 42% protein? Yet a lot of smaller less active dogs DO eat it and do fine. That said, a lot of people also say their dogs "do fine" on Purina, Iams, etc.
So, it's one of those things that only time will tell and more research will need to be done... you just gotta go with what YOU'RE comfortable with.
Grain-free brands that I've used that have a lower protein are
*Merrick's "Before Grain" Chicken
*Earthborn Holistic's Primitive Natural
*Taste Of The Wild High Prairie
...or you could go with raw. Meh, I'm still feeding kibble.. I admit it... but I'm getting there lol.