A lot of routers will let you attach an external harddrive through USB. This is very common and not exclusive to higher end models. Though with some brands, it does not work as well as with others. It allows wireless and wired devices to both read and save files on the harddrive. I tend not to use it, since I tend to access them directly from one device to the other. So when I want to watch a series on my tablet for example, I simply stream from my PC.
I5 3570 | GTX 760 | FILCO Majestouch 2 tenkeyless | Zowie FK | Asus Xonar DGX | Kingston 120 GB SSD | Sennheiser HD 518 | Samsung S24A350H