Interesting question but everyone is right that you need to look deeper into the specs.

For example my old sub was based on the Dayton Audio RSS265HF-4, a 4-ohm, 10" driver, driven by the 240W DA plate amp. Worked fine but the specs on the driver said it could handle 350 watts so no, I wasn't giving it all the power it could handle.

When the time came to upgrade my bass I considered building a new sub or buying the Ultra X-12. For a variety of reasons (time, money, etc.) I decided on the X-12 and have been very happy. Although I still have the 15" 1000W sealed subwoofer idea floating around in the back of my head