I will mainly use my computer for video editing + encode (Adobe After Effects), web browsing, watching HD movies. I only have a single Crucial m4 128GB right not, but I'm thinking of buying another one and doing this setup:
You'd see minimal performance difference at best and at worst eliminate TRIM support and have twice the possibility of failure. RAIDing SSDs generally does not make sense. Larger SSDs tend be faster, save your money and replace it with a 256GB when you can and you'll have an extra 128GB for games.