Best amp for natural timbre of unamplified acoustic instruments & vocals w/ Revel F32?

Mac 492 is a great choice.  Better yet, sell the speakers based on your post. 

I agree with the comments of John and Bill. If you find your speakers to have the intrinsic sonic signature you described (hard, thin ànd sterile) why keep them? Or to put it another way what are their attributes that would persuade you to keep them?
Charles,

Great comments, so far.
My 2 cents:
Why not contact Revel and tell them your experience? Maybe they can help direct you.

Terrible advice to get rid of the speakers . No speakers are designed to sound like what you are describing . Look elsewhere in the system . Start with your preamp . A personal experience last night . My system sounds fantastic .Couldn't be happier . Decided to buy a Krell preamp off craigs for the fun of it . Installed and my speakers are describing what you described . The Krell just does not fit in with what i got going on . Keep at it and good luck to you .

Fyi . I own a pair of Revel f30's and i find them flat and dull sounding next to my electrosats and rarely listen to them .