Already have the disc brake lock with alarm, a 1.7 kilo ABUS Detecto 8000. It's a massive behemoth of a lock, fits the Rocket. Set me back a bit more than a Xena, but I've heard bad things about the Xenas - like that you can disable the speaker by ramming a screwdriver into it from the outside, nothing like that is exposed on this one. It just requires someone to jostle the bike quite severely before it starts howling, I wouldn't mind something that actually detected that someone was standing still right next to it.