just go with what you like - there's a lot of this 'names to go with' atm, it doesn't really matter - once the child is there and the two names are said together all the time they go together naturally!
Agreed Baby Baby. I figure that the child spends the first twenty years of their live max being Madeline and baby sister, and then for the next 60 years she'll be Madeline and hubby. So in the grand scheme of things, the sibling's name really is quite unimportant. Go with whatever name you like and suits the baby.