May I suggest BIOS update, if one is available. These new generation cards cannot even work properly in PCIe v2.0 standard slotted motherboards, let alone v1.0. PCIe v3.0, v2.1, v2.0, v1.1 and v1.0 are all said to be compatible with each other, though.
You cannot be sure unless you try it. Please carefully read the return policy of the seller before you make the purchase. Maybe it is time to upgrade the motherboard, CPU, PSU and RAM as well.
Thanks for the fear alieving. Going with a used 5830 btw. I'm hoping that will keep my in good shape until I start from scratch on another computer. First step is get money, second step is spend it on shiny things.