Tube audio designs tadac (2009 version). I settled on one after owning an mhdt Havana, benchmark dac1, bel canto dac3 and redwine isabellina. The Chinese tubes should be switched out though, otherwise it sounds a bit rough with the cheap tubes. I have mine paired with an empirical audio offramp and i'm done looking.
Might do a search for the Matrix Dac Pre, its from China but I have read some good things about. Way below your price range though, $319 shipped on fleabay. And I think it offers USB. I have not heard it personally, but theres alot about it on the web.
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