Originally Posted by: scottrpileggi

The audio interface connects via USB to my late 2011 Macbook pro. FInally the output ends up from my interface via quarter-inch cables to my two studio monitors. The monitors are good size, barely used, and definitely not blown out. Music or anything else sounds great played through them.

I don't know much about Apple products! But another thought occured to me. I've never used one of those Berhringer units, so I was looking the product website. They have input level knobs & buttons for line, instrument & padding. You might also try to turn down the input levels on the Behringer unit or experiment with those channel buttons!