Combining PSU units?

[crudpuppy]

I was wondering if I could take the +5 and neg from several PSU units to a block and then from that block to my Hubs/etc

Basically just not sure if the power supplies would backfeed each other or if this would increase voltage instead of amperage like I want.

Would be nice to have 1 block to tied hubs off of and then if I need more amperage etc just add another PSU rather then trying to assign this PSU is for this 1 or 2 hubs...hehe