I haven't purchased a sirius system yet for my XF, but I did put two in my father's silverado and suburban.
I really like the Sirius units that transmit through a selected radio freq, you tune into. it really saves time during the installation. And it sounds just as good as a hard wired system!

As for the Kenwood head units, they're ok, but you can't take it with you or plug into the boom box or home docking kit. which sucks, the head unit is about $180 then you need to buy the satellite receiver which is about $100 extra. and that's not a portable system, it's always stuck in the truck.

hope this helps, I know I will be buying the transmitter version for my car!