I'm having difficulty with throughput from my Airport Extreme. I upgraded my service to Comcast Blast 150, but am getting close to that hardwired from the router and only half that or less, usually around 40Mbps, wirelessly. I had a Motorola Surfboard SB6121, and then someone on the Apple discussion forum said that it was the Surfboard not playing well with the Airport, and recommended the Zoom 5341J. So I got the Zoom, installed it, and no change. What gives?