The Setup: I just bought a kappa 120.1SE (has a rating of 300w RMS) and a sony Xplod 760w amp which runs 380w RMS at 4 ohm to the sub. The kappa is in a 1.1cu. ft. box; all wiring is the right guage, good connections, etc. Polyfil liner in the box. Amp low pass filter is set at 90hz. Gain...