Well it really depends on what you're looking for in a dog. But if you are asking for opinions, then I would say go with a dog that is the same size as your current dog, that way when they play none of them would be at a disadvantage.
Oh how silly of me, I thought the list of dogs under your post were the dogs you were trying to choose from. Wow, 7 dogs would definitely be too much for me to handle..lol