Squeaky floors have nothing to do with the hardwood on top. The plywood subflooring is moving against the floor joists, causing the squeak. The best way to get rid of that is to rip up all the old hardwood flooring, go around with a few thousand screws, and screw the subflooring down nice and tight to the joists. Walk around, and wherever you hear squaks, screw the hell out of the floor. Then install whatever flooring over that you decide on. (hardwood, carpet, tile, it matters not.)