The driver handles 10x more power, hmm? That should put it at about 5-7dB louder.
Maybe more,as the 9$ woofer was ultimate cheap no brand..
Also this horn models slightly higher efficiency...
I'll bet you've already done the Hornresp simulation
its allready CADed up! the moment i saw those DDs, i thoht id give them a try! Wgeiger apparently used some 18"s ,or was going to..of theirs. High BL high mass beasties, like big lab12s