The calculators like that provided by crown are based on the physics of sound dispersion in free space from a point source. I expect that that would apply much more to the great outdoors where you don't have a lot of surfaces reflecting sound back at you.
Dean, when you used the Crown calculator did you remove 6db from your headroom to account for reflected sound in an enclosed space. Using the 95DB in room sensitivity of the M80 would be similar but only adjusting by 4 db. Either way, you will find that your power requirements drop a lot with this adjustment. 5-6db is what is suggested or implemented in calculators out there.
I suspect that in a small enclosed room, your gain could be a lot more, and in a very open large room smaller.
Have you considered a pro amp? They give the most bank for the buck on power.
