It appears you already have a XM tuner, but if money is no object why not pick up this Sony unit?

http://www.xmradio.com/catalog/product_detail.jsp?id=6956&type=Tuner

Although it looks like you would have to mount it on the dash or something (uuugh)
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MK2a 160GB

11 Years later, these Mk2a units still rock...