There are a lot of variables that affect wireless range.
Walls, interference, other networks in the area, etc.
You don't indicate which older Actiontec you have.
Wireless capabilities also vary by Actiontec hardware revision (A,C,D,E,F,G,I).
In general, wireless range for 802.11n is somewhat less than 802.11g, even though the bandwidth is higher.
This is especially true on the 5Ghz band (which the latest Actiontec doesn;t support).
If you only need another 10 feet, you could try moving the router, or replacing the antenna with a high gain antenna.