[tonyvdb]

One thing to keep in mind with doing this outside is that you will need more power and larger speakers to get the same effect that you will get in an enclosed room due to there being limited reflection points for the sound. You will also need a much brighter projector to light up the screen as I am assuming this is going to be done in a back yard situation where there will be a fair bit of ambient light from street lights and such.

 

[tonyvdb]

Ok that would work in your situation. Have you got a budget in mind?

 

[tonyvdb]

Honestly, if your just thinking a two channel system for sound then maybe just getting something like this would do you for the audio side of things.

 

[tonyvdb]

Good quality speakers for outdoor use is a tough find. There is the Boston acoustics Voyager-7 7 There is also the Community R series I highly recommend them as I have used them for many years without issues. They are not the nicest looking speakers but preform very well outdoors.
Another option is the Tannoy Di series