Yeah, if you are on your third set of hardware and it's still not stable it might be a good idea to test with some cheap $15 RAM just to eliminate that as a source of problems. I have 16GB of Mushkin Redline 3200Mhz and some spare WD ssd had I had laying around.
As for Speedstep I'm thinking it could be down to not finding the correct BIOS settings, since the implementation is not at all simplified like most tier 1 vendors. Could also be down to using the
latest BIOS which comes default with insanely aggressive settings.