Regular CD-Audio is 16-bit/44.1K and any mp3 (320k) or FLAC made from that source will not really need to be any higher then 16-bit/44.1K.So can't really see you having a need for a DAC that can do 64-bit/384K
USB DAC do not come with analog inputs, guess what your looking for is an Audio Interface or external sound card.Guessing an Audio Interface (with it's software) is more likely to have more of the features your looking for.http://www.bhphotovideo.com/c/search?ipp=100&Ns=p_PRICE_2%7c0&ci=14834&setNs=p_PRICE_2%7c0&N=4294550051&srtclk=sort
So from amplifier to speaker, your connecting (positive) red to red and (ground) black to black.Maybe trim a little more insulation off each of the wire ends? Assuming it was a speaker issue, like one of the speakers was defective, you should at least get audio from one of the speakers.So I'm guessing the amplifier is defective.
I have the Gemini HSR-1000, which is really just the HyperX Cloud without the mic.To me the Gemini HSR-1000 is about the best headphone you could get, for under $100.If Sony put their name on the HSR-1000, guessing they could easily sell for $125-$150.