I'd set all the speakers to small with the crossover at 80Hz. That is a good setting for movies. Experiment with the settings if you'd like as Shag suggests, but for starters go with that.

the 4ohm vs. 8ohm setting on your reciever shouldn't make any difference to the sound, it just limits the current so that your amp doesn't get to hot. You'll actually get more power in the 8 ohm setting but play it safe and make sure it doesn't get too hot.

-Dave

M80s VP150 QS8s EP500s
ravenmanor.com/cinema/