Originally Posted by smudge981
That was my first thought, too.
In all seriousness, that's why I waited till my daughter was at least six before contemplating a dedicated 5:1 surround system. Sort of like Murphy's Law. ""The amount of time and effort you put into safeguarding your audio equipment is in direct proportion to the amount of damage that will eventually be inflicted upon it by an equally determined child." Going to call it "Smudge's Certainty Principle."
On the other hand, remember Murphy's Volunteer Bush-Fire Brigade Law, "If it's stupid but it works, it ain't stupid."
It is amazing the ways kids or pets can damage A/V equipment, not to mention other things. Caught my kid's hamster trying to crawl into the port on one subwoofer. Had the hamster gotten inside the sub, might have been difficult to get it out, like when it crawled down into the furnace. From then on we had to place a plastic cup in the sub port anytime the hamster was let out, because the hamster kept going back to that darn port, trying to scratch its way up the side and climb in, lol. I later discovered the hamster had been chewing on various wires around the room when my router went out. A wonder it never got electrocuted.
I still suspect the reason one of the backlights on my TV went out, was due to an impact with a Nerf football. Fortunately it was under warranty. So when it came time to put together a budget A/V setup for the basement, I purchased with potential damage in mind. Went with the Andrew Jones Pioneer line of speakers for the fronts, partly because they had strong metal grills, making them for the most part impervious to impacts. But my new BIC F12 subwoofer, I am already looking at how to rig up some kind of protective grill/mesh to the front for driver protection.
For the top of your (OP) sub, I would vote for the plexiglas option. Particularly if a glass of liquid or plant pot might be placed on the sub, might be good to have protection from any liquids that might spill and damage/warp the sub finish.