In reply to the power:
mark twight has a lot to say about all this. check out gym jones for an interesting and intense perspective.
dont forget: 'core' doesnt mean abdominals, but it does include them.
i find things like weighted pull ups where you lift the weight with your feet, overhead squats, floorwipers, turkish get ups, barbell/dumbell complexes and juxtaposing combinations (something hefty like an overhead squat followed by something complicated like man makers or burpees or a bike sprint) put it all together.
just isolating 'core' exercises like abdominal workouts etc isnt too effective - need to train entire body movements with the largest range of motion possible, which increases with training and prevents stiffening up.
oh, and keep the reps high most of the time so you dont pack excess weight. mind you, it takes time and effort to 'get big' so you will be able to deal with it.
let us know how you get on. theres not enough info about on this, anecdotal or otherwise.