Which speakers did you find bright, fatiguing or just disappointing in some way?

There are no absolutes. Everything posted so far is purely anecdotal.

I just recently listened to a speaker that sounded harsh and fatiguing on one particular amp and then simply glorious and unparalleled on another amp. Not to even mention the myriad of other components that play a role. 
It is not necessarily the speaker, it is rather how they matched up with certain components.

Mahgister, have you tried dsp?