I’m not an expert (I’m also going to be applying this year too) but other people have told me not retake it (I think I will tho since I already signed up). I also have a 1540. This is a link to the one where people told me not to retake.
http://talk.qa.collegeconfidential.com/sat-act-tests-test-preparation/2033339-sat-or-sat-subject-tests.html#latest