Sorry haven't gotten back to this, power planes are not a no go. It's just usually more helpful, at least from a signal point of view, to have two internal ground planes if you have components on both sides. If you have a good ground plane on the bottom of a two layer, no reason you can't make your top plane a power plane to alleviate some routing. One negative is you might get complacent and have have some non ideal paths of you aren't hand routing them.
