Hi

In my experience i would stay away from sites that offer paid links as these can effect  all your hard SEO efforts in one fail swoop.  Such benefits can often be short lived and can often result in gaining irrelevant links to your website and don't actually bring you any increase in traffic, PR, PA and may actually penalize your site as a result.

i wouldn't focus  on gaining x to improve PA i would  aim to gain quality links naturally and not all at once as this will also set off Google's spam, link farming alarm bells.  By gaining quality links individually and slowly it gives you the opportunity to assess the quality, and the relevancy of each one-  I know this is the slow and hard way to gaining quality links but it will pay off in the end and your PA, PR, SERPs traffic will improve in due course and you can rest assured your efforts are legitimate and don't put your website and SEO efforts as risk.

Might not be the answer you wanted to hear but hope this helps