I am not sure what defines "serious," or whether you are asking about the music or about home audio reproduction specifically, but in terms of dollars invested and system optimization, most would probably say I am at least a little serious.
From my perspective, I am fortunate to have a nice sounding system and to be done with the urge to upgrade. I enjoy listening to music whether reproduced or live, and lately I enjoy whichever system I am listening to, but I am not obsessed about any of it.