To my ears, after fw upgrade (from 1.08 to 1.10), I hear no difference in sound when it comes to SP1000 SS. We all hear things diifferently, use different headphones, and often compare by memory when you don't have 2 identical DAPs side by side with the same amount of hours on each and the only difference of fw rev in order to do a true blind a/b comparison.
I love Rudi and personally post in his group quite often, but... i have seen the same "sound update" description after every single a&k and sony fw upgrade
So, let's just leave it at that.
Btw, still need to finish my SP1000M write up (been busy at work), but after 150hrs of burn in, the gap in sound is very small. So far, many people heard SP1000M fresh out of the box after the purchase or after a dozen of hours at RMAF or other shows. After the burn in (150hrs), the biggest difference I hear is in soundstage expansion with SP1000 SS being more holographic, while SP1000M is more focused, a nice above average width but not as wide as SP1000 SS. The treble opened up more after the burn in, and I hear more sparkle now, closer to SS level.