Spraying a room with sound ...
I'm sorry but I can't really add much more to my previous detailed observations. The amplifier (and speaker) have no idea about the size of your room, or how far away you sit as they have no way of sensing the environment. They don't have eyes.
The efficiency of a speaker is measured (by convention) at 1m away, for a calibrated input power. As the measuring (or listening) position recedes from the speaker more power will be required for the same measured loudness because the speaker is spraying so much energy across the room that only a small proportion of it reaches the measuring microphone - or your ears. The reflected sounds arrive after the initial direct sound because they have to travel further (to the reflective surface, then from it to your ears) and sound travels very slowly; these reflections screw-up the clean pure direct sound which arrives first at your ears.
Increasing the power into the speaker is just not the correct way to improve fidelity; all that does is blasts more unwanted energy into the room increasing reflections and overall smear. The logical solution is to minimise the power into any speaker and sit as close to it as is considered domestically acceptable as I suggested in my drawing. As I explained, that tips the balance back in favour of the direct sound and away from the 'room sound' and completely sidesteps any issues about amplifier power etc. etc..
Pumping more power into any room - especially a lively, reflective room like yours - is not the answer at all.
That's all I can usefully say.
Alan A. Shaw
Harbeth Audio UK