The QNAP TVS-h874 has two PCIe Gen 4 slots for expansion

The TVS-h874 is the modern pick — two PCIe Gen 4 slots (x4 and x8) that can handle 10/25GbE cards, M.2 NVMe adapters, or QNAP’s own expansion enclosures. Gen 4 bandwidth means you’re not bottlenecked by the bus, even with fast flash storage. If you’re building a serious NAS around current-gen hardware, the h874 is built to stretch.