While I can't say this with %100 certainty, I'm convinced that any US Duo that hasn't been refurbished is going to need it pretty damned soon. All the black Duos, US and Japan, just seem to end up with all sorts of issues (usually audio) from the leaking caps.
This refurbishing work can be done by some forum member here for less than minimum wage on his part, but from a professional electronics store you're probably looking at a few hundred in labor bills.
Therefore a sight-unseen, never repaired US Duo (bugger the box) is worth essentially negative dollars unless you have it repaired by some crazy philanthropic mofo like BlueBMW. In that case...why not just buy the damned system from him in the first place?
Or, of course, a Duo R.