Synergy, digital glare or outclassed source are all possible sources of the problem. One thing not mentioned was how long the new ICs have been in the system. It took ~100 hours of playing time for new silver ICs to settle in on my system at which point the upper mid-range glare disappeared. They improved for another 100 hours, but only slightly and that may have just been my getting accustomed to the change in dynamics. If you've given the ICs time to break in and the problem still persists a warmer tube for the CDP might be in order. Other than that it sounds like you know the possible sources of the problem, as well as the other solutions.
Annoying Sibilance=digital glare?
I've slowly been tweaking my system closer and closer to subjective goodness, as we all do, and my most recent addition has left me a bit less than stunned. Swapped out all the interconnects (a mixture of mediocrity) with solid silver from Homegrown Audio (at the price, silly not to at least try it) and the result is a new and annoying sibilance, mainly on female vocals. It's tempting to blame it on the interconnects (sure, blame the newcomers) but I am also tempted to lay some of the blame on my front end, an AH!Tjoeb'99 with upgraded Siemans tubes, which is possibly now confronted with a downstream chain that simply outclasses it. While I’m asking for a diagnosis, here’s what downstream is: VTL 2.5, Bryston 4b-st, (w/ the Homegrown-come-Kimber KGAC knockoff throughout), Kimber Monocle XL, Thiel 2.3. -or- Headroom Home and Sennheiser HD600 - sibilance equally bad in both, if not slightly more annoying on the cans. [Long intro, now for the question:] If I put the old interconnect back between the CDP and the PRE (yes, Monster cable, though I’ve got 2-3 other’s to try as well) and that “cures” my sibilance problem (assuming it might) am I just veiling an inadequacy in the CDP which was finally brought to unacceptable levels by the much more detailed silver cables, or, is it one that we chalk up to “synergy” and declare that silver just don’t belong there? Alternatively, as I am hoping to upgrade my CDP in the not-to-distant future, is this something (the sibilance) that I can expect a new CDP to clear up? And, finally, “digital glare” is a term of art that that I have yet to put a good, first-hand, audible definition on - is that what’s setting my teeth on edge with all this hissing shit? Many thanks, (and I hope someone can make sense of this ramble...)