The theoretical limit to download 850k blocks (582,391,632,423 bytes) over 2.3 Gbps Internet is 34 minutes. After integrating shani we are now achieving 40 minutes (plus up to a minute for store build, startup, header sync, and full shutdown) on the $350 benchmark machine.
The remaining 6 minutes is largely a consequence of mmap flushing and remapping the mmap as the files grow. A higher memory machine would eliminate most of that. Also hashing will be further reduced with an avx512 box, which I just ordered for our test bench ($421).