If I understand you correctly...
This depends if your PSU is powerful enough for the additional equipment you want to run. Check the watt numbers. Don't push it too high and leave some reserve.
If you use your own cables, make sure their gauge is big enough for the needed current.
Also, make sure you get positive and negative right (polarity)
Thank you, Im probably not good at explaining things. I was talking about how the 3 that are running currently are running off a PSU. The 4th I will not be able to connect to the PSU.
I actually cut off the plug from an old electronic. So I have the part that plugs into the wall and wires at the other end.
If I match the positive and negative on the barrel connector to the plug, solder the barrel connector to the plug. Would that work just fine?