I wanna go 13th Gen and 40xx too. Why do you think the 13900k is worth it over the 13700k for FS? The only possible reason I can see besides the marginally higher clock speed would be more L2/L3 cache, which seems to be working wonders for FS performance as evidenced by the 5800x3D.
I’ll probably go 13700k unless there’s a valid FS-based reason for going for the 13900k. Should run cooler too.