I'm looking on bulknutrition.com at Optimum Nutrition Products and I see 3 different kinds of whey. They all have different nutrition information so i'm wondering which one I should buy. The MRP looks like it has all kinds of added stuff in it and it also has the most calories out of all 3. The other two seem to be the same thing pretty much with a few added vitamins in one of them. Do all of these mix with milk or what? I'm 6'1" 165 so I don't really need to put on much weight I'm just trying to build mass. Which one should I buy?