What Breed Is My Dog?

I just adopted him last week. He's extremely smart. He was housebroken by the 2nd day, and is an amazing companion to our 1.5 year old Golden Cocker. His left ear just stood today and the right ear's gettin' there. He has a white tipped tail and white tipped paws. Whereas I suspect he's some sort of Shepherd mix, I'm extremely curious as to his what else he might be.

By Ryan V.