One of my often repeated 'proverbs' is 'Where the head goes, the body will follow'. See if this works for you. In general, lead with your hips on almost all techniques. As an example, try doing a Taiotoshi, as soon as you've got contact and correct position, drive your right shoulder down to your left knee. Solid, sharp, rotation is the key.
Power is the combination of speed times mass.
Something often overlooked here is that the more speed you can get, the more power you can get. Gives you more time to develop your acceleration into faster speed. We often use way too many steps to create an attack. Step diagonally forward with right foot. Pick up right foot again, and drive it across uke's right foot.