Interfacing FPGAs to PCI or PCIe isn't hard, there are plenty of dev boards available to let you add whatever you want. The ARM+FPGA chips work well too, the I

Interfacing FPGAs to PCI or PCIe isn't hard, there are plenty of dev boards available to let you add whatever you want. The ARM+FPGA chips work well too, the IO blocks are decoupled enough from the CPU that you can add your own offload engines.