I think there is always someone better (whether individual or for the team), but on paper, I don't see many that would come in and become a regular in our front 3, at best, it would be rotation or playing with our front 3 for now.
Any players you would suggest that would push Firmino to the bench and make us a better team?
I don't pretend to know enough about other players.
However, just looking at Firmino's game, you can clearly see that other top striker's would be a bigger goal threat (e.g. Griezmann). We would require a fluid striker who fits our style of play, so it would have to be a similar player to Firmino, but one who has a stronger eye and talent for goal.
I recall that Firmino was not a big name player when we bought him. He had immense potential and we were excited at what he could do, but he essentially developed to his current level through the club. There will be others who have the potential to become a massive star through Klopp.
In any case, if we don't bring in a top forward, I think we are missing out. Sturridge will be gone, or he won't play, and Origi is not reliable enough. This is a priority area for me - even if it is back up for one of our front 3.