Tips for minimizing or reducing electronic noise?

I installed a new flat screen last night. In addition to the TV, there’s a PS3 and some computer speakers plugged in below.

I also have two small halogen lights that backlight from behind the TV to create a subtle glow emanating upwards from below the TV.

There’s a noticeable a bit of hum that comes through through the speakers regardless of the volume of the speakers. The halogens seems to amplify the hum as well.

The power outlets are by default a two prong, non-grounded outlet, but I’ve installed a grounded adapter (screwing the faceplate screw through the adapter to properly ground it) which is then run to a power strip/surge protector.

Does anyone have any advice or tips for issues like this?