"What are the bandwidth options?
The fastest performance is with 300 Mbps, however this uses the 40 MHz frequency and may interfere with other wireless devices in the 2.4 GHz band such as other 802.11 equipment. To avoid this, you can set the router to work in the same 20 MHz bandwidth as 801.11b/g equipment, which reduces its maximum performance to 145 Mbps.
For both speeds, there is an "Only" setting, which stops the router from communicating with any of the slower non-802.11n products. When the "Auto" setting is used, the router automatically drops its speed to the slowest adapter."
I'll post later where this setting is found in the manual.