In your case, rather than buying a NAS, I would rather build an HTPC/NAS directly, and install XBMC on it. It would cost you less and you could do more.

For example, you can buy a Mini ITX Motherboard with 5-6 SATA connector, then a NAS enclosure for your Mini ITX motherboard with 4 Hotswap drives and one internal hard drive ( such as : http://linitx.com/product/cfi-a7879-miniitx-nasserver-case-4-hot-swap-bays/12789), and use then the internal hard drive for your system, where you install XBMC, Web Server, FTP, ... and the 4 Hot swappable hard drives for your data.

If you want to have maximum security, you can even (with a bit of DIY) put two 2.5" internal hard drives and run your system harddrives in RAID 1.

In your case, rather than buying a NAS, I would recommend to build an HTPC/NAS directly, and install XBMC on it. It would cost you less and you could do more.

For example, you can buy a Mini ITX Motherboard with 5-6 SATA connector, then a NAS enclosure for your Mini ITX motherboard with 4 Hotswap drives and one internal hard drive ( such as : http://www.chenbro.eu/corporatesite/products_detail.php?sku=78 ), and use then the internal hard drive for your system, where you install XBMC, Web Server, FTP, ... and the 4 Hot swappable hard drives for your data.

If you want to have maximum security, you can even (with a bit of DIY) put two 2.5" internal hard drives and run your system harddrives in RAID 1.