The IA 187 is a great sub. It gets loud, gets low, sounds clear, and even mics well! The only downfall is it's mild inefficiency.
I bought a pair about 6 months ago direct from IA. I've been using them in different boxes and power arrangement ever since. They are rated at 300 watts RMS apiece, and listed as an SQL sub.
Power handling is insanely underrated. 300 watts is childs play to these subs. With a small sealed enclosure, you could easily attach one to between 800 and 1000 watts RMS. Trying this is your own risk, don't complain to me if you kill one. I have run mine with 250, 350, and 750 watts RMS to each sub. At 250, they'll get loud, but not much for DD volume levels. 350 is an improvement. At 750 they shine. To say the least, you'll need at least double their recommended power rating to see what these subs are capable of.
In a sealed box, roughly 1 cube, these subs are great for rock and metal. Crossed over at 80hz, they blend in great with midbass, and have a nice kick that most people are looking for.
In a low tuned ported box, the highs are not near as present as in a sealed, but the low end really stands out. When the bass drops, you know it. They continue to blend well with midbass, but won't really provide it themselves.
A high tuned ported box give an inbetween feel. At 35hz, the high end wasn't exactly missing, but the low end was more dominant.
Overall for the price asked for them (contact IA for info) these are excellent subs. Great build quality, power handling, and sound. However if all you have is 150 to 250 watts per sub at your disposal, you will have your work ahead of you getting them really really loud.