The IMC is on the CPU on 1366 chips, not the X58 chipset. It sounds like you've RMA'ed a lot of things. Does it crash when the system is idle or only under load? Also have you tried downclocking your memory down to 1066 and having the timings match JEDEC for that speed? Theoretically, if your IMC is to blame putting less stress on the IMC should help.
Also have you tried underclocking everything that is in the CPU? How is stability at lets say 1ghz slower than stock at stock voltages? If it remains stable at the lower clocks it very well could be your 980x. That would be a sad day.
Edit: Are you booting off the revo drive?
That is highly unlikely unless you did something ridiculous to them.