What saw attachment is used to make circular holes on back of media console?
How big of a hole? For bigger holes you can use a hole saw. They come in sizes from about 3/4" to 6".
I'd drill from the good side and go slow. The material used for the back of media cabinets is usually pressboard and it's pretty easy to "blow out" the back side of a hole.
Adam444 already recommends a great item to use to cut the holes, but I'd like to recommend a hole cover afterwards.
This is done since cutting a hole can create a jagged edge that can also look a bit unsightly even if it was sanded down.
Shown below these hole covers come in a variety of sizes, generally no larger than 2.5 inches in diameter.
This will give you a more professional look after the hole has been cut. Plus, it eliminates the chance of any cords fraying from the roughness of the hole that was just cut.
Let us know if you have any further questions,
I should have added the hole covers...
I would suggest, especially for vertical surfaces, a little bead of clear silicone under the lip the cover will help keep it in place.