Thanks, turns out slightly underclocking the RAm (776Mhz) and setting the ASUS Tweak RAM A.I. to light let me overclock flawlessly.
Really, I have everything set to auto except for the internal CPU frequency which now is 290MHz (FSB=1160). Seeing as the board itself reports as being able to FSB1600, I'd say I'm on the safe side there by far.
Also did some cable amangement, had some knot near the board and it turns out the northbridge gets really hot (at standard voltage). So I better took away any obsruction to airflow I found. Bothers me a bit, but hardly anything I can do. I'll simply trust Asus they knew what they did when they constructed that thing.
I tested the whole OC with Sandra's multicore efficiency test, didn't crash after 10 minutes, that should be enough. Okay, don't mind I never passed 40°C so I'm not worried this will be a problem even if I went at it for heavily prolonged periods.
So yeah, I'm now running well with my E4400@2.9GHz. Cheers