I've used both powered and passive setups for my backyard theater. I'm currently using a passive setup for the sole purpose of easier to setup/teardown. My sound system is a pair of EV ZX1 8" speakers connected to a QSC amp via speakon cable. Instead of having to run power cords out to each speaker, I can just run one cable to each since the power and signal are combined. Speakers + amp ran about $1000 total. The speaker stands are fixed and made of wood so all I have to do is set the speakers on top and plug in everything. I also have the Epson projector you mentioned and it's great. Not a home theater projector by any stretch, but it's bright and cheap and perfect for outdoor theater setups.