Like Brandy said, it really depends on what you are after. Sound quality (SQ), LOUD (SPL) or a combination (SQL). That being said, I'm partial to subs built by
TC Sounds. Besides selling direct, they supply
Soundsplinter with their drivers. From either of these companies, you can get a driver(s) that fit your needs.
Based on your 980w amp, a pair of 10" TC-1000's or RL-i's would be a great fit assuming your box was large enough. Can you please provide the internal dimensions? That way we can better determine what will work. And if the suggestions above don't fit with what you are after, there are other manufacturers.
-Robert