Short answer, get this 2TB Seagate drive:
http://pcpartpicker.com/part/seagate-internal-hard-drive-st2000dm001
Long answer:
You don't really give enough information about your video editing to help.
My dad's video camera uses a LOT of space on full quality (over 10GB per hour). So you need to estimate how much video you're talking about, as well as do you store downloaded videos/files, and do you intend to buy lots of games?
You also should use a program like Acronis True Image to make periodic backup Images of your SSD and that will use up some space.
*One advantage of a larger capacity drive is that it will perform better on average. The INNER Platter spins slower so you read/write about HALF the speed as the outer edge which is why defragging software moves things like Boot Files to the outer edge.
So on a 2TB drive those same files would be when the drive is 50% full and access speed would be closer to 80% maximum instead of 50% maximum.