Dawg,
> What would be better for over all sound proofing a room? Steel door or a solid wood door? <
What matters with sound proofing is mass and rigidity, so I have to think a solid core wood door would be the better choice. That said, with any door you get you'll also need a high quality seal to prevent sound from leaking underneath and around the edges. Unfortunately, good door seals are expensive. Zero International makes a line of excellent door seals:
http://www.zerointernational.com --Ethan