I have 2 Crossfire BMF12's in a small sealed box right now (about 1.2cu ft each) on a vr1000d. I had crossfire p1's before but the 400watt max and dumping 750watts into each killed one so i swapped up. The old box was around 1.6cu ft each and now the bmf's arent as loud in the smaller box. I would go with the sealed probox but its backordered really bad right now.