To eliminate the noice I have a PAC SNI-1/3.5 Minijack Ground Loop Noise Isolator from Crutchfield (
http://www.crutchfield.com/S-vRq8uUf...or&i=127SNI135 ) with a 3.5mm cable splitter to attach both the Sirius and a Belkin retracting 3.5mm plug for my iPod - and - a dual power cable from Bell to connect the Sirius and iPod power cables. When I want the iPod I turn off the Sirius. I found that prior to using the Ground Loop Noise Isolator the Sirius was hissing at reasonable volume levels - once I installed the isolator I have had no noise on either the Sirius or the iPod. Despite all this stuff in the cubby, including the Starmate 4, it all fits nicely and you can't see any of it in back of Starmate 4.
Good Luck.