Silver cable definitely works; I have the silver ray and there is noticeable extra brilliance up top and more presence in vocals (= more upper mids). Soundstage is less concave, too.
Unfortunately, the bass, which was already pretty fast (the one aspect a silver cable can improve), still has a mahousive hump in 100-200Hz range, bleeding all over the frigging place. Fiio X3 with 100Hz bass cut looks pretty attractive to this C4 owner...
I'd agree with you there about the soundsstage, mids, and the treble. Though I'm not sure if I'd phrase the quality of the bass the way you did though. I would say its more of a prominence as opposed to it "bleeding all over the frigging place". I like that blend of warmth and clarity that the C4+SPC offers, but of course that's just me.
If it matters to you the TF10 airline adapter (100ohm thingy) does somewhat tame the bass and offers a tad bit more "brilliance up top".
@eve: I have the SPC hybrid, and I confirmed with Ted that he uses the SPC as the lead and the copper as the ground. So I'm thinking that the hybrid and all SPC would be the same. I recommend just getting the all SPC cable because the copper bits in cable are already going green... #wtf
Edited by itshot - 6/15/13 at 4:35pm