If a $10 little bottle of spices could make an ordinary meat source taste like a special meat source, it would be worth every penny. This hasn't been my experience, which is one reasone that I buy meats from artisanal local sources. Even the bump in price for the cheap cuts is more that the spices would cost if they worked.
I love spice-centered cuisines like Moroccan or Indian, and like flour I grind my own spices when possible. I have a psychological block to plain-cooking an ingredient for dinner, rather than cooking a recipe. Nevertheless, my bias is that the best barbecue doesn't depend on complex spicing. Instead, one cooks an ideal piece of meat with no more than salt, pepper, and chiles, controlling the fire and smoke to the best of one's ability, and letting the meat speak for itself. This is the ideal described in Legends of Texas Barbecue Cookbook, served out the back door on butcher paper to area workers.
I don't like flavored coffees, or flavored olive oils, or dehydrated garlic and onions, and I bring this suspicion to store-bought rubs for barbecue. They remind me of the middle ages: One perhaps rightly feared baths as an infection vector, but humans smelling like healthy wild animals had fallen out of favor, so one masked with perfumes.
Nevertheless, one could generalize the idea of "umami" to any subliminal technique that enhances a flavor. And as noted above, the best practitioners of spice blending may have talents beyond us. So I'll decide one blend from the recommendations above, and try it. Always good to fight one's prejudices...