Could you have a better starting hand? The answer is no. There's no doubt that with pocket Aces you don't back down. You have to be aggressive as there is minimum risk with that hand. With the flop K,3,7, even if the other player has posket Kings, he only has two outs and he must get another K. You also have two outs, but, other 3 or 7 won't hurt your hand. Go for it!!