That's my thinking. In general I'm trying to go for the top. I got the Trident Z5 6400c32 2x32. While not the best 64GB kit available, they're pretty close since AFAIK I got the A-die. I'd expect single digit performance gain with 48 vs 64 gigs, which I would argue can be noticeable.. Check this out as example: https://youtu.be/ghJb0ttZMV4 .
Truth be told I'm already giving up performance in virtually all other games (not going 32GB way, which is undoubtedly the fastest). I just wonder whether 48 vs 64 can really make a difference. From what I've read it seems like 48 can be balancing near the edge, while 64 would providde some margin. Will probably stay with this choice.. Although it keeps bogging me.
EDIT:
As for the CPU I'm talking agnostically to focus on the memory only, the rest of the system being off topic really. You can always find a bottleneck