If you're into the idea of building a subwoofer, take a look at the TC Sounds dB-500 10" driver. For $99, you're not going to do any better. Build one of the TC Sounds recommended vented enclosures for best results, and power with the Dayton HPSA500 from parts express. If your room is big, consider stepping up to the 12" variation, which has an aluminum cone. I own a driver also built by TC Sounds and very similar to the TC-1000 12" woofer, and it is one of the cleanest sounding bass drivers I've ever heard. Someone even measured less distortion from that particular driver than from the respected Peerless XLS woofers, which were the previous low-distortion champs. The dB-500 woofers share that motor structure with the TC-1000. So, from a high-fidelity standpoint as well as an output standpoint, and a value standpoint, and as long as you're not opposed to working with a table saw, sabre saw, and electric drill, building a subwoofer is a great way to get the kind of bass you're going for. Get ready for a box that's a little bit bigger than most store-bought subwoofers, but performance that eats said store-bought subwoofers for breakfast, lunch, and dinner. Also, expect a lot of sawdust. The material of choice for box-building is Medium-Density Fiberboard (MDF), though void-free marine-grade plywood is acceptable, but more expensive.
http://www.tcsounds.com -- for the drivers I mentioned
http://www.partsexpress.com -- for the amplifier, which integrates all the necessary signal processing (e.g. crossover, phase adjustment, 1-band parametric EQ). Alternately, they have an Indigo BASH 500w amplifier that offers the same amount of power. They also have everything you'd need to finish off the project, including nifty kits which allow you to build reflex vents that have flared ends, for reduced air turbulence noise.