You mention PR5-8 sites, which mean that you are aiming pretty high. What is important in terms of link quality is that the page on that site have high PR.
One of my favorite methods for getting high PR links is to guest post on high PR blogs. The upside is that most blog owners hate having to write posts on a daily basis and view a guest post as a day off, so it's an easy sell..
The downside is that once that post drops off the front page of the site, eventually Google's spider will notice and the link value will be reevaluated.