A summary from the Sound & Vision review:

1. Loudness at 20 Hz: PSB (93.8 dB), Energy (86 dB), Infinity (84.5 dB), Outlaw (83 dB)

2. Average loudness from 25 to 62 Hz: Energy (109 dB), PSB and Outlaw (108 dB), Infinity (107 dB)

3. Bandwidth uniformity from 25 to 62 Hz:
ratio of average and maximum SPL: PSB (98%), Energy (97%), Outlaw and Infinity (95%)
difference between min and max SPL: PSB (7 dB), Energy (7.4 dB), Outlaw (16.4 dB), Infinity (16.8 dB)

Just based on these numbers, I would rank PSB (1), Energy (2), Outlaw (3), and Infinity (4).

tvd51