XtremeMac's original Luna was one of the very best alarm clocks ever designed for the iPod, but a corporate shakeup at the company effectively scuttled its official Luna sequel, and a smaller, portable follow-up called Luna Voyager was nice enough but not particularly powerful or innovative. Now XtremeMac is back with Luna SST ($130), which borrows an idea that iHome tried a few years ago with certain of its early iPod alarm clocks: a detachable speaker.…