I've read much of the threads here about crossfire problems, dual graphics, FPS issues but could not find the one having the same characteristics as I do.

My rig specs:

Motherboard: Gigabyte GA-A75-D3H
Processor: AMD A8-3850 (with integrated HD6550 graphics)
Memory: 8Gb Kingston 1600MHz
Video: Gigabyte Radeon HD6670 1GB DDR3 128-bit
HDD: WD 500Gb 7200Rpm
PSU: Inter-Tech Energon 550W

The problem starts when I enable Dual Graphics, not only that Windows 7 benchmarks stays almost the same (6.7->6.8) the in-game FPS (talking about BF3) doesn't change either (25-35 FPS on low settings). A very strange fact is that if I use the dedicated 6670 only as the primary display device the improvements are visible, I mean 40-50 FPS on medium settings. I don't think this is normal considering the fact that crossfiring the GPU with the APU using this new technology should improve the grafics not drag them down. Heres a link to prove this http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/44338-amd-a8-3850-apu-review-llano-hits-desktop-7.html

Just to clear some questions upfront here's what I've did to setup my Dual Graphics:

With the 6670 not plugged in I've setup BIOS to use the primary display graphics ONBOARD 
- Installed the latest AMD Catalyst (12.8) 
- Plugged in the discreet card and swiched monitor cable from onbord DVI to the dedicated DVI 
- Enabled in Catalys the AMD Dual Graphics option (there is no Crossfire option only this one) 

I'm using Windows 7 Ultimate x64 OS

And a helpfull (I think) print sreen

I would highly apreciate any ideas of where the problem could be.

Cheers.

Don't mistake dual graphics with crossfire. The apu's low bandwidth brings the dedicated gpu to its knees so you actually win nothing and probably get better fps using ONLY the hd6670.

Then why this technology even exists if there are no graphic improvements.

Please some benchmarks that proves differently:

And the AMD official site, whre it says this: "Only AMD Radeon™ Dual Graphics combines two powerful Radeon™ DirectX 11-enabled graphics processors to provide the ultimate gaming performance boost when you need it. Experience gaming at higher resolutions with greater image quality and boost visual performance when you combine a Quad-Core AMD APU for desktops with the AMD Radeon™ HD graphics card."

http://www.amd.com/us/products/technologies/dual-graphics/pages/dual-graphics.aspx

Perhaps in benchmarks.. but for example a few game benchmarks here: http://hexus.net/tech/reviews/cpu/46157-amd-a10-5800k-dual-graphics-evaluation/?page=2 . In some games like Dirt showdown on 1080p you get a lot more fps than on lower resolutions, but in Arkham City benchmark you actually lose some fps. So I guess its fair to say it works better in some games than others and for some it makes things worse.