🚀 go-pugleaf

I'm building an expansion chassis for all the items that
are currently plugged in the side of my Amiga 1000, to keep
them out of the way, (some I have built myself and don't have
cases), and to provide an additional power supply for them.
(The 1000's power supply is starting to complain about the load =).

The question:

I'm not quite sure how to hook up the power supply for the
expansion cards; I know the grounds need to be common,
but do the actual power lines (-12,-5,+5,+12) need to be
(or should they be?) common with the computer's supply?
If it doesn't matter, (or will work both ways), what is
the general practice for this situation?

(btw, thanks to all who replied to my thermoelectric
 module question, it was a great help!).

Thanks in advance, 
- Mike Grusin (grusin@tramp.colorado.edu)