Defeat the crossover on the Hsu and set the crossover on your receiver to between 60-80hz. Volume setting is pretty much preference. Generally you want the sub and speakers equalized. If your receiver will generate pink noise to allow you to set levels, then that's the best way to do it. Get a Radio Shack sound level meter, and as the pink noise switches from channel to channel, make adjustments as necessary to get the levels matched.
There's a recent thread around here for finding that sound meter REALLY cheap. Well worth the price...
