2007 V70 sound issue??

[BWDCBJ]

Guys,
Does my car have an external amplifier or is it built-in the radio? I don't see one under the passenger seat. The original sales window sticker says 4x25 watt amplifier???? The reason I am asking is that when i turn up the volume say 2/3 (can't tell right), distortion kicks in bad and this is with a CD. The audio controls are all set in the middle or neutral. I'm trying figure out if something is broken or not. It doesn't sound like it should to me. P.S. I have a HU-650.

Brian