Here is the build:
http://www.hometheatershack.com/forums/exodus-audio/12134-my-sealed-maelstrom-x-build.html
Couple questions:
1: Is this enclosure braced enough for this monster of a sub?
2: If it was powered by an EP2500 would there be a need for an EQ or subsonic filter?'
The bracing is fine here assuming standard bandwidth (<80-90Hz).
EQ is needed if the natural response in the cabinet is not what you desire. This is almost always the case in sealed systems; you almost always want to use an EQ to re-shape the response. And remember, a massive amp is required to EQ with success using drivers like these.
-Chris