Well, not finding a clear consensus, I took the safest route and did both. I ran both leads directly to the battery, and used a relay to trigger the switched lead on the Empeg so that the relay only passes the current from the battery when the key is on.

It solved the problem. But now that the unit powers up reliably, it drew my attention to a new problem: I think my unit may be defective. :-(

Often when I choose a certain playlist (I have less than 1 GB of MP3's loaded onto a 20 GB unit so far), it seems to lock up. It goes to the first song on the playlist I choose, shows an elapsed time of 00 or sometimes 10, and then does nothing. During this time no controls on the unit will respond, except for the pause control, which sometimes shuts the unit off and sometimes doesn't respond either. Sometimes it suddenly starts playing the song a few minutes later. Other times it doesn't, and I am forced to undock and re-dock it to reset it, at which time it works okay for a short time before doing it again. The problem is not related to the playlist itself; it will play a given playlist fine one time, then lock up the next on the exact same song.

On other occasions, it skips very badly (on the same songs that play fine at other times). This occurs even when no vibration is present (car is parked, engine off).

And twice it gave me some sort of "invalid MP3 file" error on bootup, which went away after I undocked and re-docked it.

I would say that I can't get it to go more than 15 minutes or so without some sort of error that forces me to reboot.

I shot en email to Empeg tech support but have not received a reply yet (of course we're going into a weekend). So I thought I'd mention it here too in the meantime. Any suggestions, or is my unit DOA? If the latter, I sure hope they kept a few for warranty exchanges!