This method is incorrect. This guy does not mention that you have to mess with the .bins file found on the HDD. If you just copy everything over to a 120gb then the 360 will only see 20gb (or whatever it was before). Also microsoft can see that more than one console is using a .bins file and can give out bans based on that. Yes the M$ hdd price is rape, but there is no good way around it.
This simply wont happen, along with the valhalla chips, those will not be used on this generation of consoles. Anyone who has played around with hardware mods of the 360 should know that this is not feasible.