amazons sales rank help

[Etycoon]

Hello

I read somewhere that items within the top 5% of a category on amazon sell fast. For example if there were 100000 books on amazon, all the books with a sales rank of 5000 or below would fast (Within a week or two)

My question is do any of you guys have a recommended sales rank you go by i.e the bulk of your inventory is within the top 2% of a category and so on.

I look forward to any responses.