Well, theres absolutely no reason to get anything less than 8GB these days, honestly that is more than sufficient. Since youre claiming video editing, gaming and multi-tasking, might consider 16GB, but you probably dont need it. 16GB is overkill imo. Kind of depends on what games and how much gaming. With that said, ive seen 16GB kits these days on sale for like $50-60 so....pretty cheap.. Id personally rather run 2 sticks than 4 and I didnt need 16GB so....I went with 8GB. You could always add another 2 sticks in later for 16GB as well. I dont think you have to necessarily buy a matched 16GB kit...