Haha, what an awesome and quick solution to your problems! My problems were took a bit longer to get rid of, but there you have it - the Sparrow's been "burnt-in!"
It's been a while since I've had the Sparrow and I've hated it until about a couple of days ago. Like you guys told me to, I've left it on for a couple of weeks now and have been poking in a listen here or there to see progress and just recently, it seems the sound's finally settled. And what a sound it is! Treble is still extended, but the bite to it seems to have gone, which was my main issue. Bass also seems to have settled for a compromise between emphasis and extension, leaving a satisfyingly deep sound while keeping it clean and jumpy enough to have me bobbing my head once in a while. The mids are excellent as always, and perhaps slightly smoother than before. The W1000x are now perfectly accustomed to working with the little black bird it seems, and both are performing excellently.
There seems to be something about this combo and the "synergy" it's finally created with each other. The best way to describe it seems to be as if the sound were "encapsulated" within a small but wonderfully acoustic room - a miniature concert hall, even. The music has a satisfying "reverb"-like tonality to it alongside with an "isolated" sense of space - a kind of absolute separation from outside noise that makes me want to keep listening even to the wee hours of the night nowadays (which is doing horrors to my sleep schedule and performance). I would definitely recommend anyone with a W1000x to try the Sparrow out now - just be aware that it may take weeks of "burn-in" for these to actually get sounding the way you might want them to. I look forward to any impressions or reviews that reflect or oppose my experiences.