well what speed do you pay for/expect? 16mb, 50 or 100mb? until you know that from the provider and what is actually going into your system it makes little sense to fix something that may not be broken. If your speeds are way slower than what they were the can be several causes that may have nothing to do with your hardware.
Where I live we had copper wire running from the local control box to the house, now we are still on a copper feed to the street but Telecon laid optic fibre cables and in the few weeks they were doing that our internet speed halved. So you never know what migh be causing this issue. Get in-touch with your providor and see if anything comes up.