The ethernet cables we provide with your Winston have been rigorously tested for speed and also sit very nicely in the ports on Winston.
You can certainly use your own cables, though, but we encourage you to use an ethernet cable that can handle Gigabit speeds (CAT6), and ensure it clicks solidly into the back of Winston. Some cables don't, and we'd hate for you to struggle with your setup because of it. We do not offer a way to order longer cables at this time.
The power adapter meets Winston's specific power requirements, so using an alternative power supply can cause overheating, rebooting, and/or breaking Winston. It is not recommended using an alternative.