After lots of research on the internet...
ALR-Jordan Entry S is 8 Ohm with 87dB sensitivity (1W @ 1M).
ALR-Jordan Entry M is: 90 - 10 * log10 (6 /

= 88.75dB sensitivity (8 Ohm, 1W @ 1M).
So Entry M is better suited for the Signature 15!
With Entry M speaker at 1M distance, I could get a sound pressure level (SPL) of 97.5dB using Signature 15 (I use the calculator from Crown which includes 3dB as amplifier headroom). Although I would like a SPL of 105db (usually for AV system or orchestral climax), 97.5dB should be okay for now, I need to add a sub-woofer anyways.
Anyone knows if the Signature 15 has thermal protection or over-current protection?