Not that it matters really but a hdc4 will?Just so everyone can stop being retarded with this "3inch coil for effeciency" nonsense...
AQ HDC4 Testing
There is a heads up tests of an hdc4 vs a hdc3. You can see the HDC4 has a good .5-1db for most power levels, even as low as 300 watts. It REALLY pulls away on burps when you get up to past 2k.. However, long term music on 2k the difference will probably be just as proncounced or moreso than your seeing here after a song or two.
Lasty, all high end Fi made subs won't play past 60hz, not sure how much that matters in your app, but if your looking for output up to 80hz a ZCON wont' give you that.. They are NOT SQ woofers beacuse of this, neither are XCONS , IMHO.