SSD is the way to go if your seriously into post production. One of my suites is a 27" iMac with SSD running FCP and it screams! Faster than some of the machines at my local broadcast stations...
Check out macmall for the best deals and OtherWorldComputing for the best upgrades for macs.
I would go with the last mbp over the new retina one, better deal and easier to upgrade from what I have read.