Mwilliams, I am the proud owner of a VAC Sigma 160i amp mated to a pair of Wilson Audio Duettes. Not Sofias but very very similar. The 160i is simply stunning. I will try to describe for you. My recent amp journey was a Naim Supernait, then to a VAC Phi 200 driven directly by a Berkeley Alpha DAC, now the Sigma.
The charcteristics of the Sigma is going to sound cliche but imagine mating the best characteristics of solid state....crisp snappy bass with the best of tubes, smooth articulate mid range with gorgeous highs. I have about 5-600 hours logged so far and it keeps getting better. This is the amp Kevin Hayes has in his home. The phono stage is terrific.
This amp is NOT bloomy at all.....it has prat, snap, excellent bass and it is very romantic sounding without going too far. I have installed NOS Mullard 12ax7's in the phono section and NOS 12au7's in the input stage, all other tubes are stock from VAC. Everyone has different value judgements but I believe this integrated is fabulous and it has ended my search. My setup is presently a REGA P5/Exact2, Playback Designs MPD-3/Mac Mini, Vac Sigma 160i, Wilson Duettes (no sub, doesn't need one in my largish room), Running Springs Jaco. cabling is Cardas Clear Light interconnects/Speaker Cables, Cardas Clear M power cables.
Seek out a demo, i believe VAC will be showing the Sigma at RMAF. Every dealer i spoke to about it prior to my purchase was quite effusive about the sound(when are they not!) yet I have to agree. good luck.