I think we are doing different things, so what I'm going to say may not apply to what your doing.
Take a bow stance with the left leg forward. Now turn your torso as far tot he left as possible (try to look behind you) Notice how your hip joint "seals". If you look at it, you'll see a line/crease in your pants. So, if you take the left bow and turn your torso all the way to the right, your kuas is open. My bow stance is always front kua closed, back kua opened. To get this, you have to learn how to use your spine as the pivot. If you get it, all the lower body requirements just "fall into place" The feeling is that both feet are digging into the ground at the same time.
Why is it a power position? Well, the front kua closing rotates the entire torso so you get your body weight itno every move. The back kua being opened "pushes" the back foot into the ground. You get a kinda dynamic tension between the two legs. The power comes from closing the front kua and not issuing once the kua is already closed --> it's a dynamic rather than static thing.
It gets weirder, I'm working out of the San Ti now which is BOTH kuas closed. This creates some type of a dropping-pulling power, but I don't understand that one yet. It's a hell of a shape to get though.
** The other school of thought that I know about puts the emphasis on keeping the kua in a half closed position and "pumping" the power through it while dropping the back and butt. I think this is closer to the Chen Taiji methodology byt could be wrong.