Its not just the surface area, its the Xmax(excursion) along with motor strength and stiff enough suspension to handle it.
What you'll learn later if you start competiing, a high DB score sometimes wont translate into body hurt and vice versa.
From what i see at the comps man, the SA line wont hang with HDC4s even if they have a cone area advantage. Plus in the future, if you want louder, all you need to do is to get a 3.5k to 5k amp on that sub and it'll be beyond ridiculous and handle everything you throw at it. Basically a step forward in future proofing rather than taking slow upgrades. I wasted soo much money doing slow upgrades when i could have just gotten the results i wanted with an borderline endgame setup and be happy with it.