@TS
compute your total power supply needs through link below....(results assume your using true power/80+ efficiency psu's)
eXtreme Power Supply Calculator
now if your using any "generic" psu(iMaster is also generic.), it can only give its rated power @ about 50% or less load. anything above that will cause power abnormalities like unstable voltage(speciications only allow a +/-5% tolerance of output voltage),ripple noise etc...
using non-true power/80+ efficency "BRANDED" psu will allow stable operation @ about 60-70% total load...
while true power/80+ efficiency "BRANDED" psu will allow stable operations @ 80-100% load...
remember, this still doesnt includes the protection circuits(overcurrent,overvoltage,shortcircuit,volt age spikes,sags,surges etc etc etc) only found on "branded" power supplies that generics dont have.
take note, a drop or rise of voltage, even a .1 volt, means a lot in stability, instability or disaster in a digital circuits...