Well, without a budget it's almost impossible to say. Also knowing what vehicle, location (for sizing), power available and musical style, as well as what you're looking for (soundwise)... like crystal clear bright highs, hammering midbass, etc.
For instance, one company might make the best 5" set with a clear top-end under $200, while another makes the best 6.5" set with strong midbass for hiphop in the $450 range.
All depends on the situation. No one company makes the 'best' speakers in every pricerange and every size.