C3 has the wider stage by quite a margin, better sense of imaging and a touch more separation.
Their sigs are complete different though. C3 is the more neutral soundingk, airy ,has advantage in detailing levels. It's just it doesn't have the power like HM-601 and their presentations are rather different. If you want soundstage, air, detailing and imaging C3 is the better player, though if you want an upfront, warm, full bodied, musical presentation with deep low end 601 is a better choice, rather soothing. For precision listening C3 is the better player IMO. But for just rocking listening to tunes 601 is hard to beat here. When listening you just forget about the staging and imaging because what it does it does very well
Something really addictive with this player and my T-Peos H-100. Almost taste the flavour, an essence if you will.