It'll work (connect the accessory & main feeds on the empeg together and wire them to the power feed you have) but if you do this you may well still get the speaker thump on power down as with the mk1. It will remember where it was, it has the same powerfail circuitry as the mk1.

However, a permanent feed would be good. On the old Citroen AX I had, the cigarette lighter was a good place to get a permanent 12v feed.

Hugo