Go with the Btl if you have the money. Bl if you dont.
Just run the AQ at 2-4 ohms until you can upgrade your alt.
I have A BTL N2 15 and it is extremely loud..only on 1,000 watts and it is a minium 2,000 watt sub, It would be very unnecessary to have anything really louder for daily.
My box is 4.5 cu ft net 30 HZ Birch.. I have been through many setup and have heard quite a few so i do have some experience