I just looked at a picture of the system, that has a normal ethernet port right between the optical audio and usb ports. You are probably looking at the wrong port.
If it's Ethernet it would only be 8P8C or RJ45 connector, A Cat6 UTP cable will be good enough to run a Gigabit connection. Cat5 can run Gigabit but less places sell them now as Cat6 is cheap already.
I just looked at a picture of the system, that has a normal ethernet port right between the optical audio and usb ports. You are probably looking at the wrong port.