My QNap running 24/7 anyway - I wondered why I wouldn't install a virtualbox headless runing a WindowXP License I had laying around from an old laptop... Thinking about it though, the QNap is running a busy-box based mini linux, which in no way would run any virtualbox installation.
The answer to that was actually to chroot a mini-debian, mount the device, proc, sys file systems through a bind option, and that was all that was to be done for getting a virtualbox instance running on the NAS (Atom CPU 1.6GHz, 2GB Ram, Raid 5+1).
The Windows XP system was stripped down to the minimum necessary, and as I run iTunes on it - give 712MBytes of RAM to run.
The thing is - that now I can connect all the Apple TV's I have at home without using the cloud, and have a central place running on a Raid-5 system. Exactly what I needed ! And when I buy something on the iPod, ATV or any other iTunes system, this one automatically downloads it too ...