majik, overall you are better going with matching subs, or at least subs from the same manufacturer. With matching subs you know you'll get the same sonic signature across the board, and different subs from the same manufacturer will give at least similar sound.

Having said that, I run a Hsu VTF3 mkII sub with two smaller 10" sealed subs. To me, it sounds fine. More than anything I wanted to flatten out my room response with multiple subs.

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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose