I upgraded from a Scout to Scoutmaster (and I also have the SDS). The difference is NOT SUBTLE. The Scoutmaster is noticeably better, as Slipknot noted. I found the bass is much tighter, the details much cleaner, and most importantly, the enjoyment much higher. It was certainly worth the reasonble cost ($975) for the upgrade.
I have not had the opportunity to hear the Super Scoutmaster, so I cannot compare. And to be honest, I am quite content (at least for now) with the rig I've got.