I am going to plan the building of some PA cases.

I am not sure but I think building my own PA cases will be better. I know the basic fact, that building a plain wooden box is more difficult than it seems. I know from another techy that to build a rack mount one uses "angle iorn". I have some chip board from my last build which was mostly done by another techy friend. The last project was some shelfs for a super computer. I still have the selves but sold the super computer off.