Anyone know how/if browsing speed differs on a unit like this with an iPod vs. an external HD? If using a portable 200+ gig HD has the same browsing speed for a large catalog of music as an iPod would, offers more storage space, and is cheaper, that'd seem to be the way to go. (Assuming they make them that are USB or DC powered which I think they do, although I'm not sure how shock resistant they are?)