In-game Reset (IGR) is a great X3 feature. Some dashes offer their own versions of this, but they can screw up games. Having it built into the BIOS though, that works just fine. Next time you want to switch games, try holding down both triggers, back and start if you have a huge original Xbox controller, or both triggers, back and black if you have a smaller S controller. Both work no matter what controller you use, actually, it's just that those comboes are more convenient to those controllers.
You can turn off your Xbox from most dashes, and if the one you use doesn't support that, just use IGR and hold white to do it from Config Live.
The only thing you can't do is turn it on, but that's possible with a minimal amount of wiring. Check out the tutorials at xbox-scene.com for that.