Oh don't get me wrong, the transparent cables might soften up in sonics after break-in but not to the degree that they will become a "soft" sounding cable. If you're looking for something to compensate for some aggressiveness in the treble, you may want to look into Cardas or VandenHul, both of which are very smooth and polite in the top end and to some degree a little darker than what a true "neutral" cable might impart.
I wasn't looking for a cable that changes the basic qualities of my speakers, which you may have read about on a thread a started a few weeks ago - the Axiom M80s. My only problem with them, as I think I mentioned on that thread, has been a kind of raspy sound on some tracks.
i decided to drive the speakers via the pre-out connections of a new Marantz 4023 receiver into my 7BSST2 amps, single-ended. I added inexpensive Energy subwoofer cables for these connections. These cables have an kind of RF filter on them. I didn't buy them for that reason and assumed it was a gimmick. But much to my surprise, the raspy sound, while still there, was somewhat diminished. I concluded that maybe the gimmick acutally wasn't one after all, and that I might have an RF issue in my system. So I decided to try the Transparent speaker cables which have a device on them to filter RF while changing nothing, or at least that is the claim. Anyway, broken in or not, these cables have helped to diminish the raspy sound enough that it now sounds like some kind of an artifact in the recording (echo? reverb fade?) I'm not sure, but nevertheless, the thing that was irritating me is much improved. A good example of the change can be heard with the opening passages of "So What" on The Kind of Blue albumn, where Adderley and Coltrane play in unison. What was very harsh is now, as you say, more musical.