speakers? 5.1 on g5

ok so my G5 has stock audio and the speaker in the front panel blows. I really want a 5.1 setup and i was wondering if anyone had suggestions. logitech has some nice cheap ones, but I don't think that the line out on the back of the G5 is 5.1. isn't it that only the optical audio out is 5.1? anyways, I don't have copious amounts of moneys either. what speakers do you use with your g5?😕 😕 😕