Boost site speed - configure WP Super Cache or W3 Total Cache and set up CDN

My site, located at [login to view URL] is scoring fairly poorly on GT Metrix. Yslow is suggesting expires headers, too many http requests and compressing components gzip. Google Page Speed is asking for specific image dimensions (in the code I guess) and deferred js - that one is part of the caching plugin. I have a CDN on Amazon S3 but if there's one better suited to the job, we can use that one instead. Also - something (probably one of the plugins) is causing a memory spike which crashes the site repeatedly. The site is hosted on AWS and uses Plesk for control panel - I'd like to have you review all files on the server and help me remove any that we don't need. If you are skilled with improving site speed and have feedback to prove that, you'll be on the short list. I will decide quickly and once I choose a freelancer, we'll begin working immediately with the idea of being done by early next week.