I got a new router to replace the AirPort Extreme I have. This router is the WRZ-600DHP from Buffalo. I played all night last night with configurations, and thought I'll mention a few things I came across while doing so.
When I configured the wifi with security, it removed 802.11n, making me think there was a problem with the firmware I loaded, but the issue was that the default for WPA is TKIP which doesn't support 802.11n. Changing the setting to AES fixes this.
When I added some static IP addresses to DNSMASQ, via the services tab, it broke DCHP because the configuration was wrong. I ended up finding out the issue was because my host name was mrgeckosmedia.local and the dot isn't a valid syntax for DNSMASQ.
Because the DCHP server went down, obviously my MacBook received no IP address from the router. So I was forced to set a static IP to fix which isn't hard. IP 192.168.1.2, Netmask 255.255.255.0, Router 192.168.1.1 (original firmware started with 192.168.11).
Hope this is helpful to someone starting with DD-WRT.