I bought one of these last year for my Saturn and was quite happy with my purchase. Of course it's not going to match the output you would get if you filled your whole trunk with subs but it definately gives the best output for the space it uses, as it only takes up one cubic foot and still puts out a lot of sound. With the amp built in, it was quite easy to install, and even easier to uninstall once you decide to get rid of your vehicle. I bought mine when they first came out for $244 and free shipping at
http://www.nexxon.com/infinity/infinity.htm. I see they are $269 now, but still beats the $400 price Crutchfield offers. Please note that the level of service may not be the same between nexxon and other sites, but I received my ordered item in a timely manner and at an excellent price and would buy from them again if I needed to. My only complaint was I do not believe they sent me an email confirmation or tracking number, but it was a while ago so I may not be recalling correctly. I'm not sure if they sell outside the states, and now there may be other sites that offer comparable prices, so shop around, but at the time I purchased there were not. I'd sell my Basslink since I'm not using it right now, but I liked it so much that I may stick it in a corner of my trunk in my Impala when I get a chance, just to add a little sound to the low frequencies. I don't think I'll miss the one cubic foot I'll lose in an 18.6 cubic foot trunk.
In any case, if you want a sub without much hassle, or cost, and still want to maintain your trunk space, I believe the Basslink is the way to go.
Duane