Best Dark Sounding Amp For Bright Speakers?

I would try McIntosh. There were other good suggestions here too but felt Mc had to be added. I got rid of the Krell KSA100 for the same reason and ended up with McIntosh as my favorite.

The new SA102 from Plinius is worth a try. An excellent amp, but Peter Thompson voices them with Shahinian speakers - and so they tend to work best with metal dome tweeters and need quite 'open' sounding cables. But if you get the balance right the naturalness of the sound, dynamics and inner detail are simply superb. The SA102 is more like half a SA250 MkIV than the SA100 MKIII it replaces. Dryer than tubes, but otherwise very similarly lush and full with a dose of added magic.

Room treatment!

If the speakers are the offenders why are you not considering changing speakers ? I'm not being impertinent, I'm just curious as to your reasoning.

I agree with Subaruguru -- throw some blankets and draperies around the room and see if it helps. If it does, go for some room treatments. Best spots (without knowing the specifics) -- behind the speakers (especially the corners), in front of the speakers on the floor (not too close to the speakers), on the side walls between you and the speakers and centered on the wall behind you.

Also, cables can make a huge difference as Sean and others suggest (nice offer Sean!). Speaker cables may help a great deal (MIT come to mind -- see earlier threads on dark speaker cables). As others suggest, it's tough to jump to conclusions about the source of the issue without active experimentation. Good luck.