I bought a used yggy locally and used it in my system with he1000's and grado hf-1's. My main goal was to find a dac I could hookup to my computer. I found it to accentuate sibilance in recordings, and sound overly analytical vs. my cd player. The imaging and detail were decent, but I didn't feel it did anything better than my current player and I felt it ruined some recordings. I ended up selling it.
I'm now borrowing a auqa hifi la scala II dac, which contains burr brown 1704 chips with a tube mosfet filterless analogue stage. The sound is organic, detailed, balanced in the high/low/mids and sounds great with all the music I've thrown at it. It sounds similar to my cd player, which uses bb 1702 chips and a transformer output stage, but the la scala seems to have a little more low level detail. I had my friend over and he couldn't tell the difference between the two. My only complaint is the price.
Biggie.