Lauren Maree makes an important point that we've observed ourselves with online casting---when it comes to auditioning louder is better.
Just to be clear, your top priority as a voice actor is, and always will be, to give the strongest, most competitive performances, and all the technical tweaks in the world cannot compensate for a weak audition. Having said that, however, when the casting decision comes down to you and a couple of others, sending a louder, better-recorded audition can definitely give you an edge.
By the way, for what it's worth, we've also noticed that, in general, men tend to submit louder auditions than women...
Voice Realm: "Most clients booking voice talent through online voice casting websites have little to no technical experience.
They would believe that this voice actor’s sound was inferior. You should normalize (without peaking) all sound files when submitting for auditions. In almost all jobs we see booked, the custom demo has a nice rich, strong sound."