Did you really think a dedicated line would make an improvement ?
Properly designed electronics INTERNALLY has all the necessary filters & mechanisms necessary to generate a good enough & acceptable DC. Nothing external is needed.
The only requirement from the mains is that it is reasonably sinusoidal so the transformers work properly, and the voltage stays within a reasonable range.
Unless you are driving synchronous motors, even the frequency deviation does not matter so much, as long as the frequency does not drop below a number which causes the transformers to heat up. Besides, not even the WORST mains supply in any country does not have fluctuating frequency to such a degree.