If your only using 8 of your 15, why would you ever need to prioritize plex? Do you expect to use up the other 7 with something else - if you do this something else then suffers..
BTW the plex is wired right.. Your not serving this up over wireless?
So I take it your running native firmware on that -- latest, looks like it updated a few days ago
I will have to take a look at its manual - I doubt it has much 3rd party support as of yet? But unless you have something sucking up more than your 7mbps up, and you limit the plex to 8 up then there is little reason to need qos. That is if this thing even supports it. Have to take a quick look at the manual.
edit: Well this isn't a good sign
Ok well it does have some support it looks like - page 31
There you go, you can prioritize your plex.. Have fun.. What is limited with this qos is there does not seem to be multiple queues.. I don't see anywhere to view what is going on with the queues, etc. As most native firmwares it has been dumbed down to the lowest level possible, with pretty colors and pictures as much as possible Unlikely it has much practical use other than letting the user think they have given higher priority to something over the other.. But sure looks like you can do what you want.