Ensure that you are connected to the router using a 5ghz N connection, it will be waaaaay less crowded since you have far more bands unlike with 2.4ghz that only really has 3, but be aware that even if your card says its 802.11N doesn't mean that you have 5GHZ, some are not dual band and you will be on the same 2.4ghz band as most devices.
I would also suggest downloading a wifi analyzer app on your phone/mobile device, that way you can see just whats going on with your wifi strength, interference, etc.
Then I would try and move your computer into the same room as the router and make sure the other devices aren't on or active and test to see whether or not it is an issue with your computers hardware/software.
As I said 5mbps down is...