Well, thx for the hints. I went and simulated some ported enclosures and you're right. No real gain with the horn, just a lot more space. Even the displacement is not less with the horn, so where should the improvement come from? Surely not from a driver, that has a more relaxed job..
Well, I might have to think it over, maybe it will just have to be a bigger horn, if I really want to try one. Anyway, we are moving in two days and I will actually see where I could hide two beasts in that room and think again.
Didn't get to read those technical papers, yet, but thx. for the links, I will look into them as soon as I find the time.