Hi folks! So in regards to 802.11n, here is a great access point for you to use. The cisco Aironet 3500 series of ap’s have a technology that Cisco calls CleanAir.
This allows the access points to mitigate wireless interference in heavy wireless use zones. For example if your office is located in an area where there are a lot of other wireless signals, the 3500 will allow you to have a more stable wireless network.
You don’t need to deploy all 3500 series access points either. You can deploy a few in a few choice locations and then use normal 1140 series access points for the rest.
You can read more about the Cisco 3500 series access points here.