Not sure how aestetically pleasing it would be, but this is the kind of crap that pops into my head randomly...
Get some astroturf, and a few tiny potted plants that look tree-ish. Bonsai would be ideal. Set it up in front of your entertainment center as though it were a front lawn. Then build a mini 3-sided white picket fence with some supports that hold it in place relative to the entertainment center. Make sure the fence is high enough to be a tike-proof barrier. Get a few ken/barbie dolls and epoxy them to the astroturf.
Other themes for the non "white-picket fence" folks. (As well as two halfway reasonable ideas):
Replace the ken and barbie dolls with GI Joes, burn random patches of the astroturf and put toy tanks and some small stone walls, replace the white picket fence with chickenwire.
Build two small stone walls in sections to replace the white picket fence. Line the space between them with plastic and fill it with water. Make a small wooden drawbridge on the inner wall and a wooden gate for the outer wall. Put a plastic dragon/lizard type of thing in the water.
Make the whole thing out of legos, hot-glued together. I recommend the castle series, but something done with the technics set that involved moving parts would be pretty sweet.
Or maybe you could just get some throw cushions, stitch them to a piece of elastic, and put it on the base of each speaker. Maybe something to help "tie the room together" like the dude's rug.
It also might be possible to just reinforce the cover from the back with some chickenwire or stiff metal screen.
