The Cube is cute, the district attorney in one of our rural areas just got one and I was checking it out. Looks very nice, but I wouldn't trade my xB for it. However, if I lost my xB God forbid, I would certainly consider one of these as a replacement. However, my work xB has 28,000 miles and my personal xB has 39,000 so I won't be looking for a new vehicle for a long while. Love my xB's!
Now on to the topic, I personally just use a ExpressRC, I have a dock in each vehicle and just move it around. My personal xB came with an XM tuner, but I only used it for a short while because I didn't want to have to pay for a secondary subscription. I don't know about the Nissan's radios, but know there are many alternative to getting either XM or Sirius on the xB's using the Toyota adapters. Usually it takes a year or two on new cars to before PIE and others build these type adapters. So, I suspect you are going to be out of luck for while. This is why I prefer the PNP units, cause I don't have to worry about any of that compatibility stuff. Plug and Play, no matter what the factory setup is. Though I do understand some folks want that realy clean factory look, but right now XM is your only alternative for that.