I assume you mean to get a higher-clocked 64 gb? Personally, I've never really felt the difference between different memory speeds. I've seen the benchmarks, I know the numbers. But I've never had a moment where I'm using my computer and I can say that the memory speed is bottlenecking my PC.
So in my eyes, memory clocks are quite low priority for me - I put more weight in ensuring that you have the total memory capacity to do what you need to do. Which is to say, if you have the money to spare, then sure, you can get higher-clocked memory. But if not? I don't see the problem in getting lower-clocked memory.
Additionally, if you get an X3D chip (which I assume is one of your considerations), those are known to be fairly resilient against memory clock speeds, in which case it extra does not matter what your memory clock is