Truth be told, as much as I enjoy my CX550, there are times I feel the treble is a bit much, and your assessment of the highs lacking "precision and clarity" are spot on. Fortunately, I'm lucky enough to not be hearing much sibilance, and I still have to say for the price I paid (60 quid with two-day shipping to the US. Thanks AMP3!) they're definitely worth it to my ears. As far as I know, all canalphones/IEMs in this price range have their issues, whether it be too much/little bass, too much/little treble, or recessed/overly forward mids, and these are close to my preferences. They're certainly not perfect, but until I graduate from starving student to starving schoolteacher, the CX550 are more than capable within my budget. It's also nice that they sound very similar to my favorite earbuds, the Sennhieser MX760.
Also, since this is somewhat on-topic, though I know their reviews aren't the greatest, here is semi-confirmation that the CX95 and CX550 are indeed the same: Sennheiser CX550 review - headphone reviews and video - Stuff.tv