I appreciate all the input.
For some reference on the sibilance I heard with the 1Cis: Yesterday I bought a pair of near-mint Large Advents (77'), the ones with the orange "fried egg" tweeter. I kid you not, they sound better than the 1Cis ever did in the month I owned them...well, aside from the decay factor. However, I noticed the Advent tweeters exhibit a similar sibilance with some recordings. The same applies to my EPI 100s (I have 6 pairs of speakers currently). In my system, the 1Ci tweets were no more refined than those of these vintage models.
Rest of my system is probably considered "mid-fi" around these parts. Amps are the Rogue CMII and Yamaha A-S1100. Current sources are Pro-Ject Pre BoxS2 Digital and an Acoustic Signature Wow XL turntable with Hana SL cart. Parasound JC3 Jr. for the phono stage. The most refined speakers I own at the moment are JM Reynaud Bliss Silvers - best tweeters out of speakers I've owned but not the best I've heard.
How would you guys rate the carbon tweeter against a good beryllium unit? Since I run stereo subs crossed over at 120Hz, I'm thinking I might be better off with the VLR CTs.