with what looks like 1/3 the enclosure volume of an already small AI enclosure, I just can't see that thing being more than than an overpriced midbass driver.
maybe I'm wrong
for $500, a pretty good subwoofer can be made if one has the ability to build their own enclosure. but paying someone to build you a box can easily crush half that budget, if not more.
for example:
http://www.creativesound.ca/details.php?model=SDX10 for under $200 to your door. shipping is blazing fast from CSS out of Abbotsford, and Bob simply kicks assay when it comes to customer service.
the CSS SDX subs are popular with the home theatre crowd (me included), because they sound excellent.
monoblocks that put out 200-300wRMS at 4ohms can be had for $200-250. take your pick on sonic, or even your local Visions.
like this one:
http://www.visions.ca/Catalogue/Category/Details.aspx?categoryId=54&productId=10193&sku=Z5001 for $150 + tax.
that leaves $150 to spend on 3/4" MDF and/or fibreglass and resin, along with a cheapy 8ga wiring kit + fuse holder, paint/vinyl etc.
cheap power cable can be found at Princess Auto, in the form of welding cable (if they don't have a full surplus wiring kit for cheap on their shelves), as can terminals. I've bought plenty of 1/0, 2/0 and even 3/0 welding cable there for past SPL builds for the same price audio shops charge for 4ga wire that said "Stinger" on it. sure, it's not quite as flexible or as pretty, but it does the same job for less money.
point being, a $500 budget can go a long way...