If you flash a M7820 while docked with a external monitor connected to your M6500 ATIWinFlash crashes = brickhere.
Though i wonder how you managed to brick that since ATI flash or flashrom*? ! should be able to flash the card independent of a working driver or card.
M6500s dont boot at all with bricked GPUs.indeed, crash while flashing is a bad thing. Though, that does not damage the SPI EEPROM itself and the card should still be flashable through atiflash. Of cause it won't output a picture, but that's what a second gpu is for? If the Driver keeps crashing your windows, go in safemode without drivers loaded?
I mean, if you want to send me the stuff, me swapping chips isn't the issue, but i still think you should be able to recover those yourself.