OK, well I'm looking to buy a SI Magnum 12, and I have a problem picking an amp. I have Directed 1500D that does around 1100 watts at 1 ohm, but I was looking at the Crossfire VR600D that does 600 watts at 1 ohm. I'm looking at putting the sub in around 1.75 cubes at 30hz. Which amp should I use and why? And any recommendations on the box size and tuning?