1) Size isn't much of a concern for me.
2) I'll get back to you soon about the other amps. (Put them away, have to dig them out)
Hmm, well, I knew the woofer in question was rather cheap and not exactly up to par for this kind of thing, so I suppose I will pose another question. What would be a decent driver that would be 18" and $400 or less? I'm hoping to keep wood cost to $300 or less. (Ideally, less.)
If one is going to make a simplistic assessment of the value of different alignments, it would be that sealed/IB goes the lowest, at the highest cost per dB; horns have the lowest cost per dB at the expense of size, and vented box characteristics lie in between the other two. None is inherently superior across the board, neither is any inherently inferior across the board. The one to use is the one that fits your response and output needs, available space and bank account. -BFM