I tested YBA 1, YBA integrated, AR VSi55, Copland, Shanling stp80, unison s2, unison unico i and others.
The best sounding system I found was the Graaf 13.5B II tube preamp with Graaf GM20 otl ocl (a little expensive, but worth it), this system is very accurate, quiet, smooth realistic vocals, strings, bass strings. It is magical sounding (no transformers, no capacitors) this is about as direct as it gets. If your room is large, buy the GM200 you will appreciate the extra watts, I am listening at low volumes nearfield in a 10x11 office. I have ordered the Graaf GM200 for another system, this should be amazing.
Graaf is made in Modena Italy near Ferrari, they use the best materials in there hand built instruments. I had 4 audiophiles with me when I first hooked up this amp and they told me that they had never heard an amp so transparent and smooth, after a few hours of course the ss guys when against the tube guys as usual, but even the ss guys were impressed with the delicacy of female vocals and strings. If I listened to the system louder I would run the GM20 in mono (I hear they are spectacular). It runs hot, but that is a small price to pay for that warm tube sound. My Guarneri's sing with this wonderful amp. Another collectible just like the Guarneri's.