Well....I think trying to convince Rio to manufacture and sell for a decent price a car adapter for the Karma is more or less a lost cause, I'm resolved to making my own or finding some other way that's cheap. So, I have a few questions...

1st, for the absolute easiest way around this problem, would the Karma (and dock) run off of a 4.5V supply rated at 1A?
2nd, assuming that the first is a no, and 6V would probably be a no, too, how much power (in Amps) would a 5V 3A voltage regulator require? I Can find everything else on the datasheets except that...