Alpine PDX 1.1000.........actual test values 4 ohm load, 14.4 volts, RMS output=1102 watts...........................Just post the model of the amp, it might only be like a 400w amp. And that makes sense considering monoblocks really drop off in power at 4 ohm..
If possible try to run in 1 ohm (assuming you have a single 2 ohm sub)