Gday hishutzi, i just wanted to make sure, does the box say it supports 6 screen eyefinity? I had a look at ur card on the net and i do not see this. I bought reference 7970 cards that said they support 6 on the box but they did not
!!! I know you are only running 3 monitors but maybe the card can only use 2 mini dp (I know this is crazy but it happens) The box states that to support 6 screens in eyefinity, note 1: "may require complimentary products compatible with display port 1.2 MST" so this indicates it does not natively support 6 screens, so there may be issues using all 4 mini dp at once (Or even 3, most 7970's only have 2 so this may be the issue. That it is only a dressed up over clocked reference card). Hate to say this but maybe you should have gone the asus solution, that DEFINITELY supports 6 displays (With a jumper setting on the card) and so the 4 mini dp would certainly work (I know they are a bit slower but cheaper too, and better RMA support)
I do not think this is anything to do with the mobo as the screens are detected, maybe it might be possible to get a bios upgrade for the video card?
The only other options i know is a matrox thriple head 2 go (if running 1650x1080 screens as this supports 60Hz, above this refresh rate starts to drop) or use softTH for now if you are ok being limited to DirectX 9 (As i did when i bought my 2x 7970's almost a year ago and i wanted to get 6 screens working) The first option costs approx 300 USD the other is free (software)
Also how good are the screens? perhaps they have a display port but actually use an inbulit passive adapter? Do they have dp out? Maybe try buying 3 GOOD QUALITY dp to dvi ACTIVE ADAPTERS..... That way u still have the same display speeds (this is what causes the tearing, DVI is different to HMDI, which is different to DP)
I hope it turns out to be something simple mate (BIOS upgrade perhaps??)
If you fix it let us know please