MOTM

Maybe I misunderstood the question, but when you speak of running 
multiple supplies in parallel, are you questioning whether to 
connect the + and - supply outputs together as well as the grounds?  

NEVER DO THIS!!!!

Connecting the grounds together is no problem and probably will not 
hurt anything.  Grounding is a funny business.  Chances are with two 
or more supplies, they are already grounded together through the 
panels and mounting rails.  I use multiple supplies and have the 
grounds tied together with two #12 guage wires at the supplies.  

However, it is my understanding that if you connect together the + 
or - outputs of multiple supplies that there may be a problem.  The 
power supply output is a low impedance source and any slight 
difference in output voltages of the multiple + or - supplies may 
cause a large current flow between them, probably damaging both 
supplies.

I'm not really a power supply guy, I've always just bought them off 
the shelf, but thats my understanding from engineering school (a 
very long time ago!)

Listen to Larry's and Moe's advice.  Moe has a great explanation of 
star distribution on his website.  

BTW I built my supplies into a 4 space rack cabinet external to the 
synth itself.  I connect them to the cabinets (right now just one 
but more are planned) by using large Hubble connectors rated at 20A 
and #12 gage cable.  Once inside the synth cabinet, +,- and ground 
go to large barrier type terminal blocks and from there to 10 of 
Pauls power distribution boards.  It works great.

The only problem is the new requirement for 5V.  I will probably 
leave the existing cabinet alone and wire my second cabinet for the 
three supplies keeping all the new 5V modules in there.