Try Noozoide Eizo-Rewire Pro
At the suggestion of another, I tried the free Eizo app listed above. It has many sound processor settings that you can apply separately to Line Out, Internal Speaker or Bluetooth. I love it. It also eliminates any distortion at high volumes with the proper settings. My settings for line out:
Deliver balanced, natural sound (processor enabled).
Digital Presets (audiophile)
Volume Enhancer Engine (checked...effect strength "strong")
Increase monitor size (checked only when plugged into powered speakers)
Create VSUR (virtual surround) (checked...effect.."studio II")