Best way to cut a 10-15 x 30mm slit into a 4x4 electrical faceplate?

[Now Playing]

It's time I deal with the small details around the house including my listening room. My projector's power and hdmi cables, home network cable and speaker leads for my IB subwoofer all enter a 4x4 box in the wall behind my HiFi stand. To accommodate all the cables I need to make a slit in the faceplate. I've thought of using a hole saw, but that's likely to make a mess of the faceplate. Any suggestions re cutting a neatly finished slit?

 

[Heinrich]

 

[ivman]

 

[afteburn]

 

[Now Playing]

 

[Atom8]

 

[Now Playing]

 

[darrylo]