WD MBL DUO streaming and copying soooooooo slow

Hi everybody :) 

I bought a new WD My Book Live Duo 6Tb to store Full HD videos  in it and watch them by streaming in my Laptop or Tablet.

I had a D-Link N300 (10/100) as a router, so my transfer speed was 1Mb/s (wireless) , 10Mb/s (wired) and streaming HD videos was not fluet at all

so, to have the best result,  i bought an ASUS RT-AC66U ( i know it’s not a WD, but it is number 1 in most of Top10 Routers ) , however my transfer speed became 640 kb/s and streaming was sloooooow . 

My Internet speed is 25 MB/s ( optical fiber) 

The ASUS RT-AC66U 's data rate :   -802.11b is up to 11 Mbps  

                                                                 -802.11a/g up to 54 Mbps

                                                                 -802.11n (2.4 GHz) up to 450 Mbps

                                                                 -802.11ac (5 GHz) up to 1.3 Gbps

My Laptop ( Dell Inspiron N5110 i7 )  supports 802.11b , 802.11g and 802.11n

The Question is : Is this equipment   enough to have a fluent streaming of my Full HD videos stored in the MBLD ?

                                Does it enable me to copy my files faster than before?

                                or the MBLD needs another equipment to have optimal performance ( such as my net ac1300) ? 

                             Thank you for helping me :) 

The internet speed should not affect the local transfer rate. Have you tried using another Ethernet cable? Also check the link below for some steps you can try. 

http://wdc.custhelp.com/app/answers/detail/a_id/5736

thank you very much :)