I think Im getting closer to the problem but there could be various issues;
1) Board/CPU doesnt like high HTT's and/or HTT's around certain speeds (with my Athlon X2 64 it refused to work at 266/267Mhz but over and below it would)
2) Board doesnt like too high multipliers
3) Board has an issue around Vdimm (testing now).

I succesfully ran 15x248 with RAM at DDR533. I set 13x286 and it was quite stable AFAIK. I set RAM at DDR800 and 2.16Vdimm and it all turns black after a while. 18.5x200 never really worked either And yes, the RAM does work at that speed. It's running for 30 minutes now with high Vdimm, but well, anything can happen in the next hour

I requested a RMA an hour ago and asking if I could replace it with an other board, awaiting response. That's for my 790FXB-M2RS with the blown MOSFET btw.

Ill also RMA all the other stuff and just sell them.