Thats truly Bizarre! My Pioneer AVIC-N2 with the XM Tuner sounds sweeet coming through original monsoon amp/speaker combo.
How is the sirius interfaced to the eclipse?
This sounds more like a low level impendance mismatch between the tuner (sirius)and the amp (Eclispe).
Heres a couple of tests to confirm if this is it.
Play a cd how does it sound at different volume levels?
Play am/fm radio at different volume levels how does it sound as compared to sirius.
this will either confirm or prove out sirius tuner issues.
Good Luck
