This different C class hosting, as far as I can see, is a big myth and has been answered by Google on numerous occasions. The idea comes from the fact that if you have a link farm (many many websites interlinking with each other to boost the Pagerank) it is easier for google to track if they are all within the same range and therefore easier to ban.
I've yet to see a website gain or lose placing on google or anywhere else based on not having a different C class.
This is based on what I've seen and I could be wrong, but if I am can some provide me an article or something that gives the advantages of a different C class? (hopefully not from someone selling hosting on different C classes).
That is SEO hosting niche. And if you do the search for that in google I'm sure you will be able to find something for that purpose.
In any case try to compare. What would be cheaper - take 5 accounts with diffrent IPs or take 1 account with 5 IPs.