iPod dock with amplified line out and charging?
actually you do not need amplification. Simply use an adapter like the FiiO L11 (or another cheap 30-Pin > Line-Out + USB-Power-In) an you´ll be amazed: The sound will be way louder and way, way better than the one from the headphone-out. Trust me, I made an A/B-comparison with A=adapter and B=Headphone-Out, both connected to the Line-Ins of an DJ-Mixer and hardly could believe, how much better the sound was!
Cheers from Germany!