I use a xover of 80Hz all the way around for movies (M80s, VP150, and QS8s with EP500 sub). I prefer this for movies and multichannel audio. But for 2 channel standard CDs, I usually prefer to put the receiver in analog bypass mode and use the M80s direct with no sub. This does depend on the recording of the CD as there are a few I prefer to listen to with all speakers and sub.
Good plan to get the crossover set right on the receiver, leave the sub xover on bypass (or as high as it will go to get it out of the way) and balance the level with the other channels. Let your receiver to the auto setup and then check it with your SPL meter to see that it is close to all the other channels from your primary listening position. Also experiment with the phase between zero and 180 and go with what sounds best to you with music. If you change the phase, repeat the auto setup and again double check with your meter.
After finishing the above steps, resist the temptation to turn it up if it doesn't sound strong enough. Give yourself a week of listening as you may find your ears will start to get used to the proper bass level. Certainly is okay to make changes that suit you, just don't rush them. Good luck and happy listening.
