Honestly, personally I've only eaten pork steaks about 6 or 8 times in my life. They were delicious and I/we never had nor used any BBQ sauce... It's like asking; how much BBQ sauce on a beef steak, IMHO.
Probably want about 30 bottles of a mixture of different sauces, from A-1, Heinz 57, perhaps a few with BBQ sauce in 'em...
You have to think of other people and their tastes and not just your own. What if a person likes the taste of BBQ sauce and thinks it adds to the taste of the meat? Cook the pork steaks as you like and just put the sauce on the side. I would say at least 2 gals of different sauces or 4 half gals.
Once again, you're cooking for others, and not just yourself. When I cook for others I cook to the best of my ability and let them enjoy the food as they wish.