I just installed a Pioneer Premier P690UB into my car, everything works great EXCEPT the aux-in to which I have my XM connected to. The XM unit is the AGT Sportscaster (to match the lighting style of the interior) with an in line power filter. Its connected to the back of the Pioneer with a standard (el-cheapo) headphone jack. With the XM unit unplugged from the Pioneer, and Pioneer set to AUX IN, there is a constant static type noise, a lot like hiss but not as crisp - and the problem is just amplified and dominates the listening experience with the XM plugged in. Any suggestions on how to reduce/eliminate the hissing? I'd hate to cancel my XM subscription but can't stand the hiss either. The problem is blatantly more obvious on channels with more talk (which are the ones I mainly listen to). Cheers.