Thanks for posting this review of the ES1 center and surrounds. I'm considering the 5.0 ES1 setup for HT, so this review is of particular interest.
The posted SPL versus frequency plot appears to be identical to the ES1 towers, and I suspect this is incorrect. The center speaker sensitivity was noted to be 84.6dB between 300 and 3kHz, but the provided graph indicates the sensitivity stays above 85dB over nearly the entirety of the suggested frequency band.