You focus too much on google bar
PR. This
PR is of little importance. Nobody currently knows exactly what it means (in the past, it was a pretty good measure of the amount and
PR juice of incoming links).
Just a few examples:
1. your google webmaster account has probably a
PR 8 or 9 while they are private pages without any SEO.
2. Two sites with same amount and same quality of incoming links: the first may have
PR 3 and the second one
PR 6.
3. A sub-domain of a top world
PR 9 site is not longer linked with the main site. But it keeps
PR unchanged.