I have a rig, the same as yours. Depending on the speed of your computer, latency can become a problem. You may also be rerecording your doubled vocals inadvertently every time you are monitoring them? That may be the reason why they appear louder than your primary vocals? So from what you have described, this may actually be a sound card to monitor/recording mixer miss adjustment? So even though you're using an M-box, your mixer settings, in the Microsoft mixer software application, should be set so that you are only monitoring " wave" and do not have" wave" nor " what you hear" turned up in the recording section of your Microsoft mixer application.

If you need further help our explanations, keep asking your questions with as much information as you can provide us with.

Still learning Pro tools since I never bothered to from the get-go.
Ms. Remy Ann David

What are your computer specs? Please specify a little more on what kind of machine your using.