Is NVG589 the best gateway ATT can offer?

I recently got an uverse max plus connectionand the technician installed Arris NVG589 gateway device. When I asked him, he said that the best ATT can offer. I have a 2500 Sq.ft home and this device does not get the best wireless signal to my bedroom which is on the other side of the home. I am not sure if ATT has any better gateway device, may be something which supports wireless AC dual band. 

I am ok to purchase a router which supports higher speeds (thinking about an ASUS RT-AC56R) but I am not sure if NVG589 LAN ports are gigabit ports as if they are regular port I'll probably wont get the spped I get. Also, I am not sure if I'd get the best possible speed transferred between these devices if I do a IP passthrough.