I am thinking of a few things at the moment, in the way of upgrades, and one being a pair of mains cables (UK 3 pin) to replace the ones a mate made for my S300 and SGCD a couple of years ago. They were an upgrade for the included leads Cost me £90 the pair)
Nordost Blue Heaven
Nordost Red Dawn
Tellurium Q Ultra Blue II
I am not convinced whether it is worth investing more for this particular model. Depending on the quality of electricity in your socket, I would seriously consider a power regenerator. I know it’s a big expense, but in many cases you can see a huge difference without even changing cables.