Musician vs. audiophile

P.S: It occurs to me that the 100K input impedance of the BAT amp probably means 50K for each of the two signals in the balanced signal pair, and the measured 14K balanced output impedance of the preamp at 20 Hz (assuming the Six-Pak is not installed) probably means 7K for each signal. So when the subs are connected the one signal in the balanced signal pair that is connected to both the sub and the power amp would be loaded by 50K in parallel with 50K, which is 25K. 25K/7K is a ratio of about 3.6, still not good! Also, there would be a significant imbalance between the impedances of the two signals in the balanced signal pair, given the high output impedance of the preamp, which is also not good.

All of this assumes, though, that the balanced and unbalanced outputs of the preamp are not driven by separate and independent output stages. That is the case with most preamps which provide both balanced and unbalanced outputs, but I don’t know for a fact whether or not it is the case here.

Regards,
-- Al

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.