First of all, I'd like to thank everyone for dissecting my problem.
The loudest I would need is 110 to 115db. However, I do NOT like to push the system to it's limits so at those levels I want the subs to be in "relaxed" mode and have some headroom.
If I choose to have two subs (placed in corners behind speakers) then I have 3'x2'x8' available volume for each sub = 48 ft^3 per sub
The music to be played is Classical, Jazz and Techno.
As far as HORN subs I have a big question: lets say that the internal folded horn path is 9 feet long (reasonable length). In a small room that would make the woofer be DOUBLE of my listening distance from the main speakers.
If the wavelength at 100Hz is about 11 ft, would not those extra 9 feet throw off the phase response grossly and mess up the sound at the 80Hz crossover point I intend to use???
SEALED subs: I can place stacked sealed subs in corners, lets say 4x15" in each corner. A total of 8x15" would provide enough quality vs output to outclass other types of subs for my application requirements (see above)?
I have only used sealed subs in my current system. And the problem is I cannot imagine how other types will sound compared to the sealed design.
Thank you,
Herman