Wally,
It's not just the amp that you need to take into consideration. If you already have an enclosure made, you need to determine things like the internal volume of the enclosure, the physical space available to mount the woofer (and depending on the woofer you choose, the amount of space the woofer itself takes from the internal volume).
Generally, you'd pick the woofer and design the enclosure around it, working in reverse can make it a bit more challenging. You'll need to find a woofer that will work well in the airspace inside of that box.
In addition, you will need to determine how the port is tuned and if that will work for the woofer and what you're trying to achieve for sound. Depending on the woofer, if it's designed for a sealed enclosure, it may even make sense to remove the port. There are a lot of variables.
Once you know what you'll be using for a woofer, you can determine what you'll need for amplification. Keep in mind, that if you mount the plate amp to the sub enclosure, you'll also need to factor that into the cubic volume calcuations.
Designing a speaker is a lot more involved than just tossing any speaker in any box with an amp on it, and unfortunately, if you don't take the time to figure out what works, you could end up spending a lot of money on something that will not give you what you're trying to achieve.
The sub you have linked is designed for car audio, in fact, that whole Web site is an "online car audio superstore" according to the title graphic at the top of the page.
As for resources, Google is definitely your friend. There are some free apps out there that will help you do things like plot the expected frequency response for a given woofer in a given enclosure size, assist with port tuning, etc. Well worth taking the time to grab one and learn how to use it. One in particular that I've used before is called WinISD.
Here's a link to a page that has some good info/links to things that may be useful as well, worth checking out.
Wayne's Speaker Building Page
Another thing to note, a 30' x 30' room is large. You will not get the same sort of teeth-rattling bass that you're going to get in a car, especially with just a single 15" driver. It's a matter of air volume, and how much air the woofer can move in comparison to the space in the room. You can certainly get deep, clean powerful bass with a well-designed, and well-placed sub, though.
Best things I could suggest are, be patient, learn as much as you can, take the time to do it right the first time, and above all else, have fun. The results will be worth it.
-Mike
