I'm considering purchasing a SSD drive for my 2012 13" MBP (2.5 GHz; 4GB RAM). Currently, I have a 1TB internal drive reaching max capacity (<100GB left) and the drive is running super slow. I want to purchase the SSD drive to run the OS and replace the optical drive with it. I would keep my existing 1TB drive for all of my data. 1) Would this improve overall performance (I am also upgrading to 12GB of RAM)? 2) Is a 120GB SSD drive sufficient for the OS and applications?