Although you didn't see a speed increase, did your connection speed increase when you connected through the master socket? Go to click here and choose your router then post your line stats.
FWIW extensions don't work well with up to 8 Meg you'd be better of using a cat5 network cable instead.
If you have never seen more than 2 Meg it may be that you are stuck on a 2 Meg profile...common problem. Go to click here and post the results which will tell us if this is the case. Try it early morning or late evening if it's busy.