I am not in the professional category, but I would say for an amateur, a 64* wedge is not necessary.
A 64* wedge probably has too much loft for the average player to use and work efficiently, for most, it's a waste of a club (what club would you take out to add a 64*?).
Unless you play hard, fast greens often or need an EXTREMELY high soft ball often, just open up the 60* or better yet, the 56* and flop it. I have a 64* wedge but it rarely comes out unless I am in a tournament where the greens are hard, small or very hilly with lots of break.
That's just my opinion, the only way to know for sure is to give it a shot. You may love it and use it well, that all depends on your style of play.
Let me know if you decide to go with a 64*, I may have one I could get to you cheap.