I have a custom dual 4ohm Q15 for my HT system. I built my box for my tc-3000 15 befor I got it, so I put the Q15 in. The box is 4.3cu.ft tuned to 26hz running a Hifonics BXi 1206D.....and that Q got down. Now I have the tc-3000 in the some box same amp.....I can turn the volume up more on the...