Concurrent validation and download on the big machine is obviously limited by CPU. But interesting that the CPU (2 dual 32 core 2.1GHz) is able to maintain 50% network utilization. This implies that a 4.2GHz (or 64 dual core 2.1GHz) machine would be able to entirely unblock the network (completing in 1 hour). But it also implies that if we can cut validation cost in half (e.g. with shani [10% 5x faster] and updated secp256k1 [75% ?x faster]) we would achieve the same result.