I just ordered an original tempered glass side panel for my Phanteks P400 case (PH-TGPN_P400), I bought this case when the TG version wasn't available yet so it only has the plexi window which is extremely prone to scratches (even when cleaning very gently with a paper towel)...

Now I only have to pray that I won't screw up drilling holes in the case for TG panel screws, and hopefully, it will look more-or-less like this: