be carefull with the toothpicks advice, the extra pressure might blow up the MDF since there's not a lot around the hole

 

Build a new box? The t nut idea sounds the best here imo.

 

I think I'm going to try the wood glue idea first, and if that doesn't hold then move onto the T-nut idea.

My dad suggested using a plastic anchor, however I fear the added pressure of this solution too might cause the mdf to blow. Or even if it doesn't, if the vibrations stripped wood, I dought plastic would stand up any better.

As for building a new box. There's nothing structually wrong with this box. This problem could just as easily happened to any bandpass box with a viewing window. It simply was that the fasteners wern't heavy duty enough to handle the applied force.

 

He can always predrill little holes afterward. That would help to not "blow up" the MDF....