Sensible Choice is owned by the Royal Canin company.... Website is
www.sensiblechoice.com
Dog formulas do not contain corn (they reforumulated the cat and now those do have some corn). It's one of the best ones the pet store near my house carries.... When I worked there we sold a lot of it and rarely heard any complaints about intolerances to it.
The SC Natural Blend formulas are better than the "regular" SC... But even if you are feeding the basic you could definitely do a lot worse (Iams, Purina, Pro Plan, SD, yuck!)... If the pup likes it and it's working for him, stick with it.