thfcwestlower:
JohnDuncan:I think the chips are the same, but that the upsampling is better in the 840. In practice the difference would be slight (certainly in cost differential terms anyway).
True, but you could say the same about the Cyrus DAC-X or even a Chord 64!
OP - I would stream via an Airport Express into your digital in on the cdp. Would get awesome results (imo will be better than DAC Magic, however slight). This way you wont need your pc near the stereo. Cost would be GBP 65 + an optical cable with a mini jack. Bargain.
Indeed, I just wanted to posit that you needn't get too angsty deciding between the two sonically - comes down to money and whether you need a disc player, as opposed to overwhelming superiority of one DAC over the other. Yeah the 840C is better (generalising), but whether it's 550 quid better only the OP can judge.