Are you saying that having multiple sites in different class-c's have no impact on SEO?
It would be impossible to have sites in "class-c's" as they no longer exist.
Search Engine's have understood shared hosting for longer than most hosts have existed - IP address is irrelevant in the respect of incoming links - its a "snake oil" solution ...
This has been confirmed over and over again by the SE authors, yet this "persistent myth" prevails.
* Content is the most important thing
* Valid HTML and use of correct/appropriate tags we've proven makes a difference
* Fixing internal links does affect positioning - run a test on your sites
* Response Speed matters (we've seen clients jump up 3 pages in google simply because we peer with G and the response times are therefore much better)
* Location of server (IP to Geo location) matters (several countrywise SE's will only list sites on an IP in that country)
* Incoming links and the Anchor text used, related blog posts, and so on all have an impact (affect the overall results) where all other things are more-or-less equal, but are secondary to the above.