I have a Pionneer setup that includes a Premier head unit, Premier in-dash CD changer and the XM tuner module. This is the first time I've owned Pioneer Car Audio (not first Pioneer though) and I have to say I've been thouroughly impressed and highly recommend their equipment. I've owned a lot of different brands and I would say from a quality/reliability standpoint the Pioneer comes out on top along with the Eclipse equipment I had in my previous car. I especially like the load and eject mechanisms on the Pioneer CD players. The accept the CD's very smoothly and eject them far enough so you can actually grab them. Very impressed.
I will not ever again buy another Sony car audio product. For that matter I try to avoid buying Sony anything...way too many problems in my experience. Only two Sony products I've ever owned that weren't troublesome and neither was anything recent. All their new stuff looks like crap anyway. I say pass!
AFAIK, Alpine still makes quality products. When I was buying they lost me on features and packaging. They didn't offer an in-dash changer except for the 3 CD one and it isn't XM ready. Too bad because that's the only piece of equipment they have that still looks like an Alpine product with clean lines and good looks. No in-dash changer AND XM = no sale!
The short of it is if you're going with XM get Pioneer or Alpine. If you decide to go with Sirius, the Kenwood equipment should be pretty good.
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ChuckH
"Every morning when I wake up I know it's not going to get any better 'til I go back to sleep again!" Al Bundy