The additions/ changes to the airflow are:
One more outblowing fan, on the back side of the box, protected like the ones initially installed.
The second, and far more efficient tweak was to cut a hole for the 6990 I installed to breathe out of, this effectively dissipates a third of the heat produced by the 6990, at a fan speed of 60%.
I know it's ugly, but man does it work. Had the card been further away from the case-door I propably would of have added a tube of somekind.
I had no idea on how these "stock-cooled single small red fan" -type cards cool them, untill I got this one. The solution I stumbled on is very little short of excellent. When you have either side of a card like this close to the rigs outer walls, cutting and shaping an opening that allows the card to blow out heat is very effective. I have been running the card for 859Mhs (at clocks of: cores 970Mhz, memory 200Mhz, core voltage 0.9v, stability: 37h and counting... no crashes, just havent had it running that long at these settings) at temperatures of 63-70,5c, while the outside temperatures have been swinging between 0 - 9c. I'll propably have to throttle down a bit for the summer but Im happy.
The bottom line here:
I am now a firm believer of treating dual-gpu cards with stock coolers like PSU's in regular computer cases: separate it from the rest of the airflow where possible, obviously this does not apply to open-frame rigs.I also redid the entire cable management thing whilst swapping the motherboard, I'll post a large picture of it when Im able, but atm Im holding out for the wifes camera. It's better, not good, It wont ever get good in this case : / I used ~50 cable ties, but theres simply no place to hide any wires neatly.
I also pulled out the 5830, I have no idea whats up with the card... It started getting temps of 86c nomatter where in the rig I put it. It's now running indoors in a rig labled "I hope this crap dies in a fire". Personally I wouldnt reccomend getting one of those cards for anyone. Mine is a reference-model asus, with stock cooling it was hot loud and horrible, with an arctic cooling fan it's still warm, silent and crappy. The efficiency is just utter shit. It's either undervolted or stable, never both.