I can tell you what I did in a similar situation. My Actiontek was in my loft space and 4 stories down in my basement was my Xbox 360, connected via WiFi. I was having trouble using the Xbox due to poor signal.
I originally placed two Linksys routers running DD-WRT in WDS mode to link the two together, but found it problematic for roaming.
I am now running a Ubiquiti Unify LR (»www.ubnt.com/unifi#aplr
) AP that covers my whole house with a single AP. No problems, strong signal and great ping times. For $100 or so, you can't go wrong.