Musician vs. audiophile

Czarivey, 
To answer your question of "name me one musician who likes Wilson speakers, Peter Poltun of the Vienna, Vienna Philharmonic Orchestra, violinist Wilfried Hedenborg and numerous others. Don't comment on things you know nothing about. Wilson makes great speakers: I owned them for many years. And I play guitar. Not great, but I can play it, and piano (worse, but still, I know what it sounds like). Don't be a wanker. 
Now back to the original poster: 
What's the amp? What are the cables? What is your room size and have you treated it acoustically or tested the room acoustics? I assume your wife plays her instrument in your home, so she has an idea of the acoustics, but you haven't stated this, so I don't want to go on assumptions. If your amp has a low impedance output - as I understand it - there could be an electrical mismatch. 100K output is a good match between the preamp and the amp, especially if the preamplifier is tubed.

The source hasn't still been mentioned by the OP and I wonder why.
With wrong source and cabling nothing will sound acceptable.

From my limited conversations with musicians, they prefer the sound that doesn't annoy them too much. It doesn't have to be a great sound. This means that the sound should be natural enough with low level of distortion, especially in the midrange.

i will add one additional point to frogman's excellent comment:

professional musicians don't always make a whole lot of money.  good gear ain't cheap.