Could I use legacy PCI card with thunderbolt port by the following way: I put this card into PCI to PCIe expansion, and PCIe card of this expansion into PCIe to thunderbolt expansion?
It would probably work, but I wouldn't recommend it because PCI is very slow, which would defeat the purpose of Thunderbolt. Also, I believe that Thunderbolt expansion cards are pretty rare and expensive, unless you already have one. Please note the difference in speeds of these two interfaces: http://en.wikipedia.org/wiki/Conventional_PCI http://en.wikipedia.org/wiki/Thunderbolt_(interface)
I might not have understood your question, but hopefully I did.