Well i dont totally agree on that.
NO comparison with a single R 12, either in lows or depth
Yep the 15 is louder but not deeper that 3001. Alot depends on TUning!!!
Btw i am satisfied with the 3001, if u like to hear beyond when ur ear drums start to itch badly, then mb we can get a Fi or DD but upto that it does fine.
Btw Rolla is getting, 2x15" type Rs wired to 1 ohm on F2500d