Ok, I hooked up my very old, very crap Toshiba DVD player with analogue connection straight to my amp. I also connected it via optical, through through the marantz streamer and then into the amp. I then proceeded to put in one of my brightest CD's - Groove Armada's Greatest Hits.
Usefully, I could easily switch between the two inputs while listening, without having to pause the music at all. So there was no memory loss apparant when making the comparison.
And the differences? Subtle. When listening through the Marantz, there was just a touch more presence to the music. It was ever so slightly more full sounding, less recessed, slightly more bass and (maybe) a hint more treble...but I may be confusing treble for detail here. By comparison, the analogue straight from the dvd player was slightly more congested and distant. But I am talking TINY differences here. If I didn't have the benefit of switching between the two sources on the fly, I'm not sure I would have noticed any difference at all, such is the fallibility of hearing memory.
Rather worrying really, how little difference there is between a 12 year old, very cheap dvd player and a £700 (at launch) streamer with dedicated hi fi DAC in it. Perhaps something like an Arcam Irdac will have a similar step up in quality again over the Marantz, putting that bit more air and detail into the mix. I would hope so. But it seems like a vain hope, especially in light of the above.