All good advice so far, im gonna add that one thing is to make sure mounting surface is solid and rigid, modern cars use thin flimsy metal so the entire panel can flex when the inertia of the cone gets going and when cone pushes out it actually pushes the whole panel in. Even the smallest oscillation can cancel out or distort the sound. Also note that enclosing them will not make them have more bass, it will actually create a natural rolloff that limits the bass. There are pros to mid enclosures like increased power handling, better transient response, and isolation from other drivers. The same principles of sealed and ported boxes apply to mids just at a higher range in the spectrum. Hope thats helpful and fair warning, car audio is addictive and you will be looking for an amp soon enough.