Though with the Pioneer IP Bus you can get an IP Bus to RCA converter that costs 40 some odd dollars.
I'm inclined to believe that this converter is to add RCA in to an IP-Bus head unit, not to add RCA Out to an IP-Bus device like a tuner or changer.
At various times, I've had the Pioneer, Sony Plug and Play, and Delphi (my wife used to work for XM). The Pioneer is what's currently in my wife's car hooked up as an FM modulated unit. The sound is too bass heavy and muddy, but I don't know how much of that to blame on the modulator. The display is crap, and will only show 10 characters IIRC and won't scroll.
If you want RCA out, your only options are the Sony and the Delphi. They both will have car docks that come with tape adapters, but they both can just use a headphone jack to RCA converter cable.
Years ago, I swore to never have anything to do with Sony products again, yet I ended up with this unit somehow anyway. It reinforced all of my negative feelings about Sony. Screwy button layout, obvious features missing, only 5 presets, unreadable screen, same limited non scrolling display as the Pioneer (although 12 characters, IIRC). The latest plug and play has upgraded the display to be readable, but I don't know if it scrolls. I think it has the same limited presets, and no direct number channel entry.
The Delphi SkyFi, though, is everything I ever wanted. It's smaller than the Sony, but the display is four times bigger. It doesn't have a loud fan like the Sony, yet doesn't get hot like the Sony did. The display is the best of any XM Radio. Huge, and readable. It has the ability to see what's on on other channels while continuing to listen to the current channel. And, it easily pops out of the car to take in and listen to in the house.
The installation can be more unobtrusive than the Sony, because it can go on the front of the dash, instead of just on top of it. Plus, the cradle has a standard size mounting connector that can mate with all sorts of other mounting options.
I can't think of a better way to add XM to the empeg, unless someone were to hack up a tuner port to IP-Bus interface or something. Now that I think about it, does anyone know how IP-Bus or AI-Net or any of these other protocols work? Is it some sort of low speed serial communications tied to line level audio transports? Because we've got the serial port, the line in, the serial lines in the tuner plug, the audio lines there, the extra interface lines in the Patrick tuner, etc.
Even if those buses don't resemble RS-232, has anybody ever seen a hack to interface serial to one of those buses?