Recently, my cable internet access has been upgraded to 15 mbps download speed. My Mac connected to the router via ethernet gets 17 mbps. My iPhone gets close to 15 mbps when connected via wi-fi to the router's network and to the dLink access point/extender. My wife's Mac when connected to the router via wi-fi gets around 12 -13 mbps and is only getting around 7 - 8 mbps via the dLink. The signal is best from the dLink, though. What gives?