Take OneStop Systems presented an external PCI Express solution at the IDF.
The heart of the device is a Host Adapter that extends PCIe outside the PC, via cables up to seven meters long. This card is already available in the US for 295 Dollars. It sits in a PCIe-x4-slot and so extends the four lanes of the bus. So, you can use other x4-devices to connect externally.
OneStop showed off a RAID system, that really benefited from the 10 gigabits per second PCIe connection.
There´s also a switch available, kind of like having eight extra PCIe-slots outside the box. For validation, or stress tests, this seems like a nice solution.