What he needs is a router with at least 300mbps wan to lan throughput, a wndr4500 is way more than his requirement (wndr4500 is about 800mbps wan to lan and cost $200). A wndr3700 will do just fine and its costs about $40 on ebay and it has 340mbps wan to lan which is perfect for his requirement.
Edit: His lan to lan transfer will never reach gigabit speeds, because I bet his hard drives or even ssd are the real bottleneck on his lan to lan network. He will need at least 4 ssd in raid0 in two computers on his lan to transfer data at 1gbps between said computers. He will need $1000 worth of hardware for that to happen lol.