Oh, Maddie is so cute!!
I don't think you could pick wrong for one thing....these puppies are so adorable. You will probably want ALL of them!
But, I too fell in love with Sophie and really wanted her from the first moment. I wasn't sure that I was going to get her or her sister when I visited as there was someone else who had already scheduled an appointment before I did and would be coming the next day to pick which female he wanted. I told the breeder which one I hoped to get and she e-mailed me the next day to let me know that she was mine!
These things have a way of working out just right! I would say anytime from 4 weeks on would be good though!
Good luck!