There is a certain limit to every audio equipment, if you cross it, there would be problems, there is a certain volume limit at which the system is tuned, if you cross that, there would be distortion.
Ive tuned my system to be optimal at 30-32 out of 35, at 34 i start feeling a little distortion, that because ive crossed the line.
120watts of clean power is enough for this sub, i was feeding my pioneer 306 with around 140-160 with the kenwood M845, and it would play really well, even though it was in a sealed enclosure, not a ported.