I'm glad you rescued Max but sounds like you need to find him a home. You really need to meet the breeds you are thinking of and read up. If you don't have room for a GSD you DON"T have room for a Boxer (I know I have had to rearrange some of my life for Tyson the energizer boxer) I have 2 newfies and he wears thm out and still has go power. Most all young dogs will be full of energy, I might suggest an older dog, they are calmer with age ,but remember some DO NOT ever slow down.