TREO SSi10.xx if you want a sub choice, but I don't see why your DD wouldn't keep up.
Neil Pert??? Really??? J/K He's good I just don't like Rush. Some other drummers to look into would be Vinnie Paul whom (PANTERA) I'm sure you've heard of, My personal fav> Justin Foley from Killswitch Engage- has a masters in percussion, Andols Herrick from Chimaira, David Svenson from In Flames. Today there's a lot of fast talent out there.
But back to the subject on hand, borrow a sub from a friend, don't care what brand, just put it in there and see if the sound that you're displeased with changes. It shouldn't be to hard to change the port in the box. Study how they have it constructed and add to it if need be or try to remove it to shorten it.