All this does beg one question, though (for undeducated souls like myself): if the DACs in the SP1.7 had 192kHz operation enabled, why would that actually be a problem?
If the source material is 192kHz, then it may very well be the case that it won't sound as good as the same recording would do if it had been mastered at 96kHz instead - but how many people actually own both 96kHz and 192kHz versions of the same recording? As it stands, anyone who actually does own any 192kHz source material can't play it at all on an SP1.7 - which has got to be worse than playing it with a high noise floor.
Similarly, if the source material is not 192kHz, then surely what the DACs are doing when playing it back will be exactly the same as it is now, regardless of what they might do in 192kHz mode?
I can see that you might get some grumbles from people who have some really fancy up-sampling equipment for intelligently converting 48kHz signals to 192kHz on the fly - but that's not going to be very many, and all you have to do is say "it'd probably sound better if you only upsampled to 96kHz actually."
So what's the issue? Does allowing 192kHz operation actually adversely affect 96kHz operation?