Many thanks to everyone who gave their input in the comments section of my last post. I have spent the last few days nearly reduced to quiet whimpering, rocking-back and-forth-in-a-corner-madness over this decision.
The lines of the chair are such that it would look spectacular in any of the wonderful colours available in the Kvadrat lineup, (and, as some of you noted, anything beats its current tired fabric), but in the end, I decided on #640 (a favourite with many of you as well.) I adore rich purple shades and think that this will integrate well, be forgiving when it comes to inevitable signs of wear later on, and provide a nice injection of dark glamorous colour.
I was hoping that my chair would be reupholstered in time for Christmas, but no such luck! The job is scheduled for early January. Ah well, we have waited this long, a few extra weeks of waiting will be worth it in the end.