Sure an ASUS or equivalent router with USB and cloud support will work. Nah, my router stays as my router and should concentrate on doing a great job at that. At most, setup as a makeshift seed-box. Besides, for security, I would avoid hooking up a main backup drive to a router, no matter how much claims the router makes.
*Routers have been known to be hacked or contain malware, they'll easily spread to my drives, corrupt em or worse, have sensitive files uploaded to anywhere.
*RAID support on NAS
*The router will likely keep the hard disks spinning non-stop and external hard disks are not built for 24/7 spinning.
*More security, speed and flexibility.

For now till budget, time n space permits... Plug n play.