Buying a PR6 Ranked Website

301 redirect counts the same a link from that domain.

normally it would not transfer more pr than a link from the homepage of that domain would.

this was explicitly mentioned by matt cutts (should you choose to trust what he says).
I did exactly what you said about using Open Site Explorer (I have a Pro SeoMoz account). The domain authority is 58 and the page authority is 64. Seems legit to me

review the top links manually to see they aren't spammy (e.g. viagra, porn links, senseless scrapebox blasts etc).

seomoz statistics are very easy to fake with spam links. people who look at them without further introspection are plain suckers.
How much is the site cost? If alot, I suggest buying a brand new domain of your own and then use the money to buy High PR linkback to your site.
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