Got one ABS unit from a wrecker, tested the ABS unit on both cars and problem solved! No more ABS light, brake light, and power steering light, and speedo works again. Thanks guys for the great help. And I was lucky it was a plug and play replacement, no reprogramming is needed. But still puzzled why both RX8 ABS module died at the same time, and I didn't even mess with car's electrical past many weeks.
Now that I have the bad unit, will try to open it up and fix it for the other car.