@TitanTy,

Do you happen to know what speed your ethernet cables are rated for(CAT5/5E/6), and if they are passing through a network switch?

You could try to use that wire to the main deco and wire it directly to the PC to see what speeds you are able to get. You will also be able to check the negotiated rate to see what bandwidth the wired connection is capable of.

It may be that the cable is only rated for gigabit speeds and is simply maxing out. You could also try setting a high priority device for the PC in your QoS settings to see if this will allow your PC to connect with higher speeds, however I highly doubt it will help.