Everything matters.
I have experimented with several power cords.
generally speaking the better the equipment and the power supply, the less you need exotic power cords.
However, all of my equipment has some level of upgraded power cords.
That said, if you stream, I highly recommend a high end network box to clean up your Ethernet signal. I have used the UpTone Audio Etheregen and love it. Easily matches any power cord upgrade I have made for less money in most cases.