Quality PBNs are clearly the best, then probably followed by aged web 2.0s. But if you're starting a new site, targeting low-medium competition keywords, and have no aged web 2.0s so can only build new ones, can you still rank? I'm talking about something like, new Web 2.0s as tier 1, hit with SER using contextual links and some filters like Pr of domain and number of obls, and then contextual links from SER with less stringent filters for tier 2, like PR1+ and a higher number of obls. Then a blast to tier 2. Also, how many links would you point to each tier, and how many links to your fresh money site? I also take it that it would be better to build up a network of web 2.0s to start off with for all the niches you're thinking of targeting in the future, instead of creating new web 2.0s every time you start a new money site.