I've just read (albeit translated) the Audinst review which seems to follow the theme of many others in that it can be a great little DAC/AMP if with some very minor changes.
That said, it was hard to understand (probably one of those things 'lost in translation' ) what the differences in terms of sound quality are between the Topping and the Audinst and how you felt about them in comparative terms.
I listen to a lot of varied music from Jazz, Classical , Female/male vocals, dance and so on (so most things!) - I very rarely listen to heavy metal or extremely bassy music. I love the Sennheiser 580s I have but am also a fan of clean, controlled (hate loose/wooly bass), detailed, accurate and 'open' sound.
Not that it is a major consideration (as they are both affordable) but, in the UK, the Audinst would cost me significantly more (70% or so).