Cheap Dell server, dual socket, with lots of PCI slots. Or, dual Xeon motherboard ($200 on eBay) with low power Xeons. Two CPUs and sockets mean more lanes. Add

Cheap Dell server, dual socket, with lots of PCI slots. Or, dual Xeon motherboard ($200 on eBay) with low power Xeons. Two CPUs and sockets mean more lanes. Add that with $30 pcie boards and you have a decently cheap NAS.