I'm planning to buy a [TP-LINK TD-W8961ND](http://www.tp-link.com/us/products/details/cat-5512_TD-W8961ND.html) modem+router and two 8dBi TP-Link [TL-ANT2408CL](http://www.tp-link.com/us/products/details/TL-ANT2408CL.html) antennas. I'm going to attach the two 8dBi antennas into the modem, because this modem has two external connectors.

* How much coverage will I get for this configuration in meters (if the antennas have no interference)?
* Since I'm adding two 8dBi antennas will I get 16dBi antenna gain?