I have an HP z440 running Windows 7 Pro. There is no more drive space available in the case. I'd like to use this computer as a NAS machine. Yes, I could add usb drives to the computer but usb is so slow. What do I need to do to add an external SATA drive? What enclosure do I need? I assume I have to add another SATA controller? Which one would you suggest? Thank you for your help.