The cheapest and easiest would be to simply install dimmer switches for each set of lights.

There are some automatic systems out there that you can control with a universal remote, but if it's not too much trouble, just stand up and adjust the lights when the previews are playing.

Just a simple halogen torchiere floor lamp will work great.
The light shines upwards, so it won't interfere with the picture.
Be sure it uses a dimmer switch. Don't get a regular Incandescent bulb torchiere. They don't produce comfortable dimmed light.