Neal 
The pro slot is for video cards that would work on 25 to 50 watts which I haven't ever seen. There is plastic block to prevent you from misalligning your AGP card. I wouln't even worry about having this feature. I have both an Asus Slot A board and the Abit KT7- Raid and love them both.  Either board will be a fine purchase.
                                        Good luck
                                        ski