facts:
1) JL F113 is a fine sub for what it can do in a small sealed box
2) give ANYBODY (manufacturer or DIY'er) 3000USD (cost of a F113) and they will come out with a ported design that will trump the F113 in THD, GD, PC, FR.
3) subwoofer design is always about tradeoffs.
4) you don't have any measurements to prove that the JL F113 will best ANY ported subwoofer.
why don't you come to where I am and let's do a shootout, I have these:
yes, there's a sealed DD18 in there.