Multiple Class C's are important if you have multiple sites of a similar theme (ie: if you have 10 sites about fruit you need different C's, if your sites are about fruit, cars and stereos then they can share the C, or IP even)
Some resources you might look at are
www.adultsem.com (several articles and tutorials)
www.adultsem.com/adult-seo-blog (look for the article on building an SEO friendly site from scratch)