Yes, it does improve with the Sbooster, after the mod kit is fitted on the Mini it will now allow you to plug in different PSU's, I prefer the sound out of the HDplex 200.
I think just the mod kit can be purchased from Upscale Audio, something to bear in mind is removing the IEC socket out of the Mini the red power wire must be cut, so pay attention how you do this, in case you need to return the Mini in it's original form.