Best Loudspeakers for Rich Timbre?

Well, to me there is a problem with this whole notion.  I mean, different instruments will their produce their signature timbre at different frequencies.  Is this not correct?  Wouldn't a flute's timbre be reproduced at a higher frequency than a cello's? 

If this is the case, then I'm not sure it's wise to go for speakers traditionally considered to have a "warm" sound, because that may entail being rolled off in the high frequencies, which might auger against the ability to accurately render the timber of a flute or piccolo. 

It seems to me that one should look to acquire speakers with the most accurate response over the widest frequency range.  Now, if one only listens to a certain type of music, say for example, chamber music, then it might be possible to pick a speaker based on it's abilities in the associated frequency range.

+1 @mtrot  

different instruments will their produce their signature timbre at different frequencies. Is this not correct?

It seems to me that one should look to acquire speakers with the most accurate response over the widest frequency range.

If I am imagining right what you have on your mind, Sonus Faber would fall into that category.

Sonus fader anything from Amati Futura and backwards.  Vienna Acoustics.

I don't have a specific recommendation but I do think that the OP wants very high performance level. And the rest of the system, including recordings, should be up to this as well. $50k set-up for a medium size room ? At least.