Jian thanks for the impression comparing the Solo to the 801 and the C4. So far, I have been playing with the Solo pairing several of my amps (Protector, Mustang, Pico Slim, and the SR71b), I have also been playing with the Boomslang and comparing to the Solo internal Dac. I have also been comparing nano 6 to the Ipod Classic 6. I don't feel like I can't draw too much conclusion yet but this much I can say is 1, the Nano 6 by itself sounds better than any other ipod classic that I have heard but if you pair the Solo with the Nano 6 and Ipod classic 6, the advantages disappeared. The two ipods sound very very similar and that is good and that is what I expect. 2. when I compare the Solo internal DAC through analog out to my Boomslang through the Coax out, and because they are not straight up comparison, they sound awfully close to each other in terms of sq. There are some slight differences that I haven't been able to put my finger on but it will require more critical listening. So far, the Solo matched my expectation and it is a worthwhile purchase. It really bring desktop performance level to the portable setup. I am very happy. I will update my impression as they become available.