Options for retrofit of existing Clarion/Sirius system to Garmin545 XM

[tfc]

I have a 2007 Chaparral 256ssi that came with a Clarion M455 and Sirius. I would like to add a Garmin 545 and take advantage of XM Marine weather, and play XM music stations through my exisitng sound system.

Anyone know how much of the existing Clarion I have to change? I know I need a new antenna for the Garmin and that the 545 can receive both XM marine weather and XM music stations, but can the Clarion M455 be wired to accept the satellite radio signal from the Garmin? If I have to change the head end of the Clarion, so be it, but is there a version they are making now that will work with the Garmin 545?