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If there is a 301 already in place then you have nothing to worry about. Google won't see it as two different pages. As for the PA variation, this is a very minor variation and nothing to worry about either. I would only be concerned if your non www site had a much higher PA than your www site, then you may be redirecting the wrong site. For instance, you wouldn't redirect your PA55 version of your domain to the PA12 version. Hope that helps.