Just set up my MARANTZ NR1501 av receiver with the CANTON MOVIE 80CX 5.1 speakers i used the amps auto setup to set the speakers which i know isnt perfect. It asked me to set the subwoofers volume at halfway and the crossover at its highest, i guess thats to protect the rest of the speakers from lower frequencies. but does that mean that the sub will be supplying all the midrange as well as all the bass? should i be lowering the crossover and is it safe to do so?