Who has XM and who likes it? Who has Sirius and who likes it? Which is best? I've been eyeing the XM2 Go, but would like something that also doubles as an MP3 player. All I want is flash card capabilites, like an SD Card. To be able to pop in a 1 gig SD card in the XM2 Go and use it as an mp3 player also I'd be set.