Ain't it for Replay gain? ?
I add my files by drag and dropping to the "Now Playing" not through the library.
I've heard Media Center takes care of distortion too.
I'm sorry, but I don't think I understand.
You said the volume is low. You also said the volume set to 20%, which should sound low.
You said you have DSPs disabled, but then mentioned Replay Gain, which is a DSP. Replay Gain will turn down the volume of most music. This is expected.
If you still think there's a problem, please describe it in more detail.
Thanks.