I'm not sure there is a specific answer to your question ... there are too many variables for each system so you just have to test different slider positions. (on both soundcard and jriver) -- totally un- scientifically, it seems to me there is a trade off because you are boosting latency in JRiver which is your direct link to your DAC -- and personally pushing jriver beyond 200ms I
"perceive" on my setup has a negative effect on SQ -- as stuttering is not acceptable, you will have to make a compromise - I would start at no more than 300ms for jriver (they recommend 100)
As for your USB DAC you are already at the absolute maximum of USB spec (5 meters) before you can start experiencing packet loss. It seems logical to me that adding extenders and powered hubs would not at all be recommended (for sound quality) but then again I have read otherwise (and I am no expert) ... as long as your connection is in asynchronous mode (otherwise you can have jitter "issues") I am going to meet with some guys that work with Linn next Monday and I can ask them what they think
You might want to google Hydrogen Audio for the USB question -- (they shoot people for posting BS on their forum
)
Is this the wrong place to post this topic?
You might want to split this and re-post your USB question in the Sound Cards, DACs section where people more knowledgeable might see it easier