My D-link has measured up 9M with no issues, I think even over 10M once. Anyway, if you run a speedtest, what are the results?
Are you using the same network cables or new ones?
If you log into your router and go to Basic>internet>manual configure:
What do you have for internet type?
Is primary and secondary DNS servers filled in?
is "use intercasting" checked or unchecked? Try both and test.
What is MTU set at? should be 1500 for cable.
Under Advanced>Advanced network:
What is your WAN port speed at?
Under Advanced>Game fuel:
What is "connection type" set to?
If auto change to 1000Mbps and test.
If set to 1000Mbps, set to auto and test.