I had the same issues when auditioning the def techs in the showroom. I found that I could manage the brightness of the speakers by using the recievers EQ t0 tune the treble to -8 to -10 db while adjusting the mids to + 6 db and the bass to + 4 db with the internal subwoofer gain set to 12 oclock (7002's). It was a little to much tinkering for me to buy em but I was able to tune them quite a bit. I am sure you have tried just about everything but if you havent shot the wad on the internal EQ give it a try they are forgiving to significant changes in EQ settings.
IMO 30-40% of the highs were muted in the showroom whe the curtians on the wall behind the speaker were there. When I pulled the curtian the high became overwhelming. The take away - put an old T-shirt over the back of the speaker to see if it mutes enough of the highs to make em work. Not audiophile but may give you enjoyment until you change.
I think my room acoustics and speaker placement are pretty good, so maybe that's why my DefTech speakers sound great to me.
I can see any speaker sounding bad with bad room acoustics and bad speaker placement.
Oh, and I just have to say that I hate using any kind of tone controls!
I think if you need tone controls, then you need different speakers.
