Still not a definitive conclusion but i think i burned one two:
Sapphire A1351000 Dual X 3GB with boost (but not runniing boost, or only short time, did not hash any faster with it) out of two deliverd recently (one on the 8th and one on the 11th or so of February) one of them is probably the cause for my system crash last saturday. I did smell something occasionally in the beginning but not lately. Cards were both plugged directly into the pci-e slots. First week i did not run 24x7 as i still had some linux config work to do to get it all working. After that it ran 24x7 with auto-gpu and the highest thread concurrency (around 20k) i could set and ran them in sgminer with I=17 at around 550kH/s. Idle power was 65 watts and mining at 580. Recently i saw that climbing to near 600. The top card had 3000 RPM listed and the bottom one half (could be software as well? ) and they showed 74 degrees Celsius in the software. Top one seems to have died.
At the moment the screen goes black after it tries to launch the Linux graphical desktop, if both are powered i wont get that far. Bottom card on only succesfully boots. Had some trouble with the HD as well until i plugged it in with another sata cable and sata port on my mobo. So maybe i fried the mobo and/or PSU as well. Gonna plug the 7950 into my Win desktop to see what will happen then.