SEO Spyglass - need some pointers

Hi,
I posted this in another thread but I'm not sure if it will get enough exposure for somebody to answer my questions so I'm going to post my own thread.
So in order to find out if my keyword will rank in the top 5, what factors should I be looking at in Seo Spyglass to make my decision to go forth with building a site?
What factors in Traffic Travis should I be focusing on prior to running Spyglass to run further checks?
High PR + Age and the number of back links to the page?
If site A has a lot of back links (lets say in the 1000s) on site B that has a PR of 5 and you want to outrank it for a particular keyword, would a smaller amounts of back links on a PR 6 website or higher make that happen ?

Appreciate any info thanks.

better quality backlinks can outrank low quality backlinks...sadly there is no numbers its all about testing...
about the decision its all about your own criteria...a real competitor is someone on has a good onpage seo and a lot of backlinks pointing to his/her site...