Depends on the wireless the device has. Your router supports 450+450 for theoretical max of 900Mbps. I don't know of any consumer tablets or phones that can do this. Most tablets and phones top out at 65Mbps and some are now doing 130Mbps. This is to conserve battery, and really for a tablet or something those speeds are overkill.
Now your Internet speed is at max 50 from wow. Wireless does have overhead and is effected by how many clients are connected, so assuming you have 50 Internet from wow, you may not get your full bandwidth on wireless unless the device supports 130 or 300Mbps. If I recall correctly the real world throughput on 65Mbps wireless N is between 30 and 40 usually. And just under 30 on wireless G.
So to wrap it up, your router is capable, but the devices may not be. You can upgrade laptops and desktops to get full speeds, but tablets and phones and the like are limited by their hardware.
So assuming your nexus 7 is 65Mbps wifi (not sure at all) you should see between 30-40 when doing a speed test on it.