ASUS RT-N66U - 900Mbps Dual Band Wireless N Router

The highest speed you should expect to get using the RT-N66U is 450Mbit/s. The 900Mbit/s rate is what's called N900, and is not a speed which is actually possible, it's the speed of the 2.4Ghz radio and the 5Ghz radio combined.

Beyond the 450Mbit/s mark there are a few things that play into the actual connection speed. The first is the WiFi card in the device you're using the connect, this is one of my personal pet peeves on cheap laptops, the WiFi cards that are slow! There's also interference, this is a particular problem with 2.4Ghz in built up areas. And then beyond all of that there's a heap of other issues, one of the reasons why when you call tech support they tell you to plug your laptop in using ethernet (something that's becoming harder to do with the proliferation of tablets and laptops without ethernet ports).

Hope that helped you understand why you won't get 900Mbit/s out of your router, despite all of the above it's well worth going for a router like that as the quality of service you get from it far exceeds most other consumer routers.