Another way to check RAM is to run it at a lower than its rated speed and see if you're problems clear up.
I had some terrible OCZ Gold DDR3 RAM for X58 that caused crashes all the time. It always passed memtest, but turning it down to 1066mhz solved all my BSOD problems.
i7 processors (possibly just the older ones but I doubt it) hate >1.5v RAM I've noticed.
I still need to replace mine with 1.5v...it only runs at 1066 also despite being 1600 at 1.65v
And now I'm no longer primarily a PC gamer. *shrug*