Actually 64 wedges are usually lob wedges. You have a 52 and a 56 then your starter lob wedge. Any of the three will function in the sand, but i guess your 56 wedge would be your sand wedge. If and when you want to swap out the starter lob wedge you would want to look for a 64 wedge. On here most people don't get too concerned with the degree or name of the wedges. They are more concerned with the rated distances and how evenly spaced they are. Players on here who are running a 3 wedge setup usually try to space the three wedges out and have the first wedge spaced out evenly with there PW in their iron set..
For example, in my bag my pitching wedge is rated at 120yds. So I have 3 wedges at 100, 80 and 60. They happen to be at 56, 60, and 64 degrees. Other people like to have a 64 wedge at 50 yds then go up to 75 or 85 then up to 90 or 95. Every one has their preferences so just find wedges you like and try to use the same premise.