acctingman,
I have exactly the same problem as you did. I am trying to upgrade my HP h8-1160t to AMD 6970. I have bought a Seasonic PSU. But, there is no signal, and the system will not boot with the 6970 plugged in. This is the case with 2 new 6970s.
GPU-Z suggests the PCIe slot on our motherboard IPISB-CH2 is 2.0. Our cards are PCIe 2.1. My default AMD 6570 is also PCIe 2.1. So, the BIOS should support our card.
One thing I found funny is: I booted Windows with the on board integrated graphic. Then I plugged in the 6970. Windows recognized it, but installing the driver requires reboot. Upon reboot, there is no signal again, and the system will not boot.
Do you have a solution now? I would appreciate your help.
Thanks,
Xiang