+1 for the Schiit Loki. I have the original, and using it slightly foreshortened the sense of depth, but otherwise it had little detriment effect to the sound.
Like others have suggested, I did switch my preamplifier- from an old Audio Research SP6B to a Cary SLP05 with ultimate upgrade, and the need for the Loki to tame the high end tizzies on some recordings went away, so I no longer need it. But it did work wonders at taming the hot top ends of poorly mastered recordings (like the High-res anniversary edition remaster of the Chicago Transit Authority- ouch!)