Crazy idea while reading the QNAP wiki: install a custom OS on my QNAP TS-451
Turns out is not that hard! (if you are willing to lose your warranty..)
All I did was open the NAS, remove the drive cage and disconnect the QNAP DOM (512MB USB storage connected to a internal 9pin USB connector) and then it booted from any USB, like the unRAID usb key
Time to put some drives in this baby!