When you speak of USB-powered DAC, I had in my mind a Schiit Fulla priced at $79 - not this:
http://www.head-fi.org/t/729686/ultrafi-dac-41-r2-r-ladder-dac-priced-dropped
I would be interested, if I had not just finished chasing my last non-burrito DAC. Looks interesting nonetheless...
It's not the dac-41. Ultra-fi came out with a newer dac- it is just a do it yourself xmos usb (latest model) receiver chip to a PCM5102A chip to rca outs. Simple as that. No power source and it weighs almost nothing. About 1/20th the size of the yggy. I think it could be built for aroiunf $100 in parts for someone who knows how to do it.