If you can afford that TRELOCK BS450, you can afford the Kryptonite Evo Mini AND locking skewers to secure the seat and wheels. The locking skewers are a pretty darn good alternative to buying a separate lock or cable to secure both wheels and the seat. Skewers: http://amzn.to/11vKMS4
I've used the Evo Mini combined with skewers for over a year now and nothing has been stolen. I often lock up outside, including sometimes overnight. There are plenty of bikes locked up in my neighborhood with missing wheels, seats, handlebar grips, brakes, etc.