So. . .
The essential debate seems to be whether more performance can be had by throwing gobs more money at your subwoofer. It would be truly sad if the answer is no.
However, terrific performance can be had with DIY projects. The appeal of them is the fact that you built it with your own hands, saved a ton of money, and can have great performance that will impress all that hear them. Subwoofers are an excellent DIY project.
Or, you can go out and buy the most expensive unit and be done with it. The pride here is taken by having the best there is and that you obviously have plenty of disposable income, which is impressive. Your friends too will think you the bee's knees, as they say over the pond. This would be the Robb Report approach.
How much is the last 2% or 5% or 10% worth? It's a personal decision based on individual values and means. That said, others probably don't care that much about the last 2% and won't appreciate having it lorded over them, especially related to their own systems.