At the moment I am looking at buying some kit from overseas. I am under the impression that all of the internal computing parts such as the main circuit card, secondary gfx cards, HDD, DVD-RW, and CPUs universally run on the same low voltage DC ouput (usually +12 V and +5 V) which is the same emanating from all PSUs, meaning the only difference in computing parts between AC and DC countries is the PSU itself, everything else is interchangeable.

This hopefully means that I should be able to buy any internal computing parts from any other country except the PSU which is the only part which has to accord with the local power standard be it AC or DC. Is my information correct, or are computing parts less universal than I think?