You'll never get the results you seek because you are not willing to address the causes of the brightness and you reject the cures. You have a very large room and you use very inefficient speakers. Your room's surfaces are very reflective, yet you use a wide dispersion speaker. Acoustic rooms treatments - can't do! Equalizers - won't do that either! That leaves you with only one possible way out -- a preamp with built in EQ. Check out the various current and past model McIntoshs. But be warned, it's still a band-aid type solution. The mismatch between your room and your speaker is the real problem.
It would immensely help if you would post your system and include several pictures of your room.
It would immensely help if you would post your system and include several pictures of your room.