Although it might change slightly because the ambient noise will affect the wattage required to overcome it, what you will find below is what levels you will get based on the ceiling height and tap chosen for your speakers.

On the 1.5W tap at a listener height of about 6' the SPL would be approximately 92dB (91.76dB to be exact). On the lowest tap available for the F-2352C, 0.5W, you would get 87dB.

Ideally you want to be 10-15dB above ambient noise level for intelligibility. I have included a chart on sound levels and perception examples. 

As for the recommended D-class amp, since we do not have a 3 channel model I would recommend the DA-250FH (4 channels of 250W @ 70.7V).  We also have a 2 channel unit, DA-250DH (2 Ch. of 250W @ 70.7V).