I'll also say the BG over slate soundboard is the best out of the three, but the aluminum and glass soundboards are still smoking calls that aren't far off in sound. You can't go wrong with any of them, and if another pops up for sale, no matter the soundboard, if you want one you better jump.
Unfortunately like others, mine are not for sale either. But keep an eye out and when one comes up be ready to snag it.