I've lived in KC since I was 7 years old...there are lots of good BBQ places, but Fiorellas Jack Stack remains the best in my book. And I remain incapable of duplicating (or even really challenging!) their ribs! Man, they are good.
There's lots of great places though. The Gates sauces, which have a nice thinner bite to them compared to other sweeter sauces, are great, but I usually just buy them at the store and use them with my own BBQ. Smoked whole catfish basted with Gates BBQ sauce? Maybe really weird, but also really good! And I like it better with really hearty meats like brisket, the vinegar cuts through more than with the general Kansas City sauces. But I do like Jack Stack sauces, they have a more complex flavor than many.