I would reccomend 7-8 Cf with 112-128 inches of port area tuned to about 38-40 hertz. you see that high tuning and think well i want lows... The hdc3 Will give you amazing lows at that tuning and will be loud as fvck. tuning to 34-37 will Be Very very low but not as loud. While The copper coil HDC3's will take plenty of power, up to about 2500k daily if you know what your doing and feed it clean power. While the aluminum can take even more, They are made with the intentions of 2k+ and are capable of alot. Ive heard people talk about the copper coils being more musical than the aluminum and vice versa. Imo its not really an audible difference while some say that the aluminum have better Sq to the fact that aluminum is lighter there fore alloqing the cone to mover faster as well as aluminum being able to decipate heat faster than copper which means better cooling. To power these beastzzz you could probably be fine with a AQ 2200 on a copper coil either at .5ohm or 1ohm. Those amps are fine at that impiedance just dont be stupid. The aluminum will be louder on the same power as well. but if you are going with the aluminum, either the AQ2200d at .5 ohm or the 3500d at 1ohm will push one perfectly