Michael,
Thanks for the tip on how to remove the metal grill. I've looked at these speakers now for awhile and could not figure how to open them up without damaging them. And I like your idea of using bolts with washers to mount the brackets, that sounds like a winner.
Your thoughts concerning the MDF confirms mine, I don't trust that material to hold screws over the long haul either, and the last thing I need is to drop a 15 pound speaker on someone's head. It might damage the speaker.... lol
I was trying to avoid shelving, hoping to make the installation more professional looking and "cleaner" by use of wall brackets, so at the very least I am going to open up one of each and take a look see on the inside for clearances for mounting bolts.
Thanks very much for the advice, and the tip on how to open up the case without damaging the speakers.
Bill