Sony's manner of claiming DR and BW is disingenuous to be polite. Yes, you can have a frequency response up to 100kHz if the DAC post filter cuts off at that frequency. However, when measured from DC to 100kHz, SNR will then work out as about 30-40dB on account of the noise content above 20kHz. If your replay chain will handle it without causing noise fold-back it won't sound like 40dB because you only hear the bit up to about 20kHz and measured from DC-20kHz, an SNR of 120dB is indeed practical. I cannot help feeling uneasy about the fact that on the one hand they feel the need to claim a bandwidth up to 100kHz as if that were to be audible, while relying on the non-audibility of the noise beyond 20kHz in order to claim 120dB.
So far my feeling remains the same: 50kHz suffices. I'm not alone in this, nobody makes DSD gear with a 100kHz bandwidth. As far as the impact on amplifiers etc goes, it is this HF noise I'm speaking of. The ringing on PCM converters does not increase slew rate and causes no issues.
The situation as it stands now is this: if you are unsure about what format (PCM or DSD) to record or mix down in and your only interest is in sound quality, do not choose the format first. Under no circumstance should conceptual arguments come into the discussion, like how much it seems to resemble analogue etc. This is immaterial. A circuit that "has a certain philosophical rightness to it"* and that performs inadequately is, after all is said and done, still a circuit that performs inadequately. The only thing that counts is how close the output signal sounds to the input signal, taking into account other requirements like cost, portability, work-flow etc, to the extent that they are important for you.
So. If your workflow permits DSD, this only means that you have a handful more product offerings to consider compared to your PCM-only peers. Other than that, ignore the format and choose the converter or recorder based only on sonic transparency. The Korg box makes an excellent excuse for using DSD (usually to convert to PCM as soon as you can though) because regardless of format it is an unusually good sounding location recorder for the price. As non-portable items are concerned I can think of only one converter worth the hassle of recording in DSD but modesty prevents me from naming it (now there's a shamelessly immodest statement if I ever saw one). To use the Korg as a mixdown recorder strikes me as odd because there we're not interested in how good it sounds as an affordable portable recorder, but how good it sounds compared to anything else you'd normally use in this application.
In principle going from DSD to PCM or going from one sampling rate to another is a perfectible process. If Korg claims its DSD to PCM process is better than sample rate conversion they probably mean compared to hardware SRC's which have all sorts of practical limitations. But a good off-line converter like Izotope's SRC doesn't have those limitations and if Korg's is as good, well that's as far as it goes either way.
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*The person at whom this snipe is aimed knows who he is. Should you be reading this: get over it, man. I'm keeping a couple of beers chilled in the fridge for you to talk things over.
