If you have a pair of speakers that you'd like to install outside (or anywhere else) then go buy a Power Node which is the same as your Node but has amplification built in.
If you don't have speakers to install outside (or anywhere else) take a look at Bluesounds powered speakers (There's 3 of them) to place around the house. They don't have an outdoor rated speaker so whatever you do for the outside you'll have to pay attention to the weather.