After putting in a Kenwood DPX-502 which is GREAT, I found it impossible to find the Sirius or XM boxes made to plug directly into the Kenwood head unit. Sirius and XM both recomended the one that uses your anteana. Kind of defetes the purpose of having a direct plug in sat ready radio no? No one stocks either adapter for some reason, all say out of stock or back order including crutchfield, best buy, Circuit city, etc.... I tried them all and notta, zip, nill.
Ebay store called SOUNDSGREAT had the Kenwood adapter and Sirius box and it plugged in and worked right from the start. I also have the BT box so the sat box plugs into the BT box and that plugs into the headunit and now my headunit displays the sat station and info as it was designed to do without another unit mounted to the dash somewhere to do the tuning which is one of the reasons I got the headunit. I could find the XM Kenwood adapter but no one has the XM box it plugs into to plug into the radio, some marketing work is needed by both these and Kenwood to get it straight. All advertise on their sites about the boxes but they almost don't exist. Weird......
If needed, go to ebay and search for
"SIR-KEN1 SIRKEN1"
This kit is $94 and it installs in less than an hour (45 min used to route antena

)