Lots of discussion on this topic at EphBlog.
http://www.ephblog.com/archives/002649.html
Short answer is that being a legacy is worth about 50 SAT points.
Tough to tell about your case without more details. Aggregate SAT score is useless since writing score is largely ignored. What was your verbal? How competitive is your high school and where do you rank in it? Where did kids with similar ranks from last years's class go to college?