Hi everybody! I'm new here. Anyhow, I've read a few posts around the web re: rear speakers for the City Express. The premium stereo does has a fader in place for rear speakers. Has anybody determined if the wiring is already in place back there for these back speakers to be installed? I'm VERY interested to know! Also would be interested to know if my Chevy dealer could upgrade to four channel sound and perhaps a subwoofer if I purchased one from Crutchfield or an online vendor. BTW, I'm a huge fan of the satellite radio system in the Chevy City Express - the selection of stations makes the miles of driving most enjoyable!