Quality backlinks push your site higher
External links are hugely important for your SEO campaign and the better the quality the more they strength they will give.
The search engines view external linking like a popularity contest so the more high quality links (high PR) the better the vote. So for example one PR5 link will be better than lots of PR 0 links.
What you also have to remember is that the search engines like these external links to be built up over a period of time so it’s a natural thing rather than being automated with lots of false links. So taking your time and progressing naturally is the optimum way of increasing your sites popularity and rankings.
Remember it’s a marathon not a sprint and this is how the search engines see it!