Do CPU voltages matter when upgrading ?

Each CPU requires its own specific voltage, which is approximately the "rated" voltage, but varies slightly from CPU to CPU, even if the CPUs are the same model. At boot-up, the BIOS reads a code from the CPU that tells it what voltage to set for that CPU's proper function.
If you updated the BIOS to cover the CPU model you want to install, then the BIOS should be able to automatically detect and set the correct voltage for that CPU.