Topic: Japanese USB headphone-amps / DACs any good?

[jpk]

Hi! When I searched the web for 192kHz USB headphone amps I found some japanese products: Rasteme UDAC32, Rasteme RUA22A, Ratocsystems RAL 24192UT1 and izo iHA-21 (I find the izo a bit expensive, and I prefer the look of the Ratoc over the other devices, but sound quality is more important to me than styling). The specs look similar to the Asus Xonar Essence One and the Teac UD-H01, but the japanese products are smaller and I don't need much of the features Asus and Teac offer: I am only interested in the sound quality of the DAC & headphone amp through USB. I don't know much about the op-amps, d/a-converters, usb-receivers and all the other chips involved, and I don't have the opportunity to audition these devices, so I hope you can give some recommendations based on the used chips or even on listening experience! (I am planning to buy good headphones later, for now I will use my 70 Ohm rated HD-25-1.)