In reply to:
The EP500 is very flat in the same region, ie is effectively 3-4 dB higher at the 20-25 Hz range.
Actually the EP500 b/w 22-35Hz also varies by about 3dB. The EP600 varies by even more.
However the nose dive of the curve does not start until beyond 15Hz for the PCUltra 16 while the sharp dive begins at about 18Hz and 20Hz for the EP600 and 500 respectively.
Whether a consumer will notice these slight differences, i'm not sure, but the change in volume is at a level humans can perceive. With the notes being so low on the frequency scale, it is hard to say whether it would be picked out consistently.
All these subs are excellent in their performance. Price and aesthetics are primary remaining factors in my opinion. Personally i think both these options are overkill for music unless one enjoys that dance club beat or runs the units at about 10% gain.
