The sub doesn't really need to be timbre matched like the rest of the speakers. That said, since you have a lot of volume to fill, I really don't think that 10-inch sub you have can crank like you want it to. It's a fine sub, but just isn't big enough.
Check out the offerings from
Hsu and
SVS. While there are other companies like Velodyne, VMPS, Bag End, and others that make quality subs, to get a sub in your price range, you're going to end up with a product that won't have the performance of a Hsu or SVS. Besides, VMPS would require an external amp, despite it's goodness.