NAS would be an option although I usually like to circumvent additional complexity. For a home user managing additional boxes with other OSes and there quirks means lot of additional work.
Always reduce complexity, whenever possible. NAS and RAID are not suitable for home systems, where there is not an IT person available to make sure they keep running properly. If you do use RAID, the only one that makes any sense, at all, is RAID 1 (mirror), but that is likely to cause more problems than it prevents. Note that RAID is NOT a backup scheme, although many people seem to think that it is.
Having said that, I built my own eCS 2.1 based NAS box, It works great, and I do know how to run eCS.

I only get terrible low performance with samba.
If you have the right combination, SAMBA works okay. The problems seem to be in EVFSGUI (not sure about Netdrive), not in the SAMBA server. I use the SAMBA server (running under under eCS) with windows, and it is rock solid, and fast. I can't say that about using The SAMBA server, or Windows 7, with EVFSGUI.
I do use RSYNC for eCS backups to a local hard disk, a local USB connected hard disk, or a 1 GB LAN connection (my home made NAS), with wonderful performance, and results. I have been considering using a USB disk to emulate RAID 1 on the home made NAS, but I haven't got around to that, yet. It might work better if I just used a second hard disk, but the box doesn't have room for that.
VBOX can not be easily transfered to other machine as all you get is wrong 'CPUID'. At least I didn't find a way until now.
VERY EASY. Open VBox, do File-> Export Appliance, select what you want to export, and do it. Transfer the results to the new VBox host (any platform that has a reasonably close version of VBox), open VBox and do File-> Import Appliance. When it is finished, you have your system transferred. You probably do need to tweak a few things, like machine names (so there are not duplicates), but the appliance thing does change the CPUID and MAC address for you (read up on it in the help).
Corrected RAID level. It should be 1, not 2.