I went with one of these-
Amazon.com: PolyPlanar MRD80i AM/FM/Sirius Satellite Ready/Internal DMD Dock: Car Electronics
It works with my already existing Sirius
antenna, and I also didn't have to replace any of my amps or speakers, just like any other
marine stereo system. Works well with my complicated multiple speaker zone set up as well. You can hook up to it in numerous ways, for instance I keep a 64 gigabyte iPod in it with a lot of music on it, but also have an auxiliary cable run so I can plug in anyone elses
phone, tablet, or other device quickly and easily as well. The IR
remote is great, and it's nice to be able to control the iPod by
remote without fiddling with it, though the controls do take some getting used to. All in all a nice unit.
The SD card slot is also a pretty nice option, since if you don't already own a high capacity outdated iPod you want to dedicate to stereo duties you can get a large SD card for much less
money and dump all your music onto it instead. After all who buys an iPod instead of an
iPhone anymore?