An ADSL router would have been best.. do you have the Actiontec pk 5000 connected to the wan port on the tp link?
This is wrong.
Look at the dhcp settings on your routers,
make sure the tp link has a management ip in the same network range that the actiontec pk 5000 would give to computers. then turn off dhcp on the tp link.
Make sure the action link is connected to the LAN ports on the tplink, not the wan port..
This will leave you with the Actionlink working as the DHCP server/ internet gateway, and the TP link acting as a gigabit switch/wireless access point.
Yes an adsl router would be better but this would be fine. It's what i did before I got fiber.