[SOLVED] External Graphic Card.

I bought the "i-tec USB 3.0 Dual Display Adapter", downloaded the beta drivers from your link, worked like a charm. But it was some kind of laggy even everything being usb 3... Also video stuck on the internal (notebook) screen... unplugging adapter and the video was fluent...
Well, it seems to work but I'm not sure if this is really a good solution.
But your information was very useful und in general it did what it is supposed to do. :'D
Thx.


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Edit:
I don't know what the issue of the performance was, but I tested it some days later (without further changes or "trying to solve it") at home with two other screens, no issues. I guess I restarted the notebook or so and this solved my problem.

My experience / Summary:

I bought an i-tec USB 3.0 Dual Display Adapter for about 55 USD.

You need one free USB 3.0 port and get 1x HDMI and one DVI, this DVI port also supports VGA.
Included is a DVI to VGA adapter, a USB 3 cable and common stuff (manual, cd, device itself,...)

You can use the DVI and the HDMI port at the same time. So it's easy to use dual screen with a notebook.
The device has also a power socket, it is only needed if your HDMI/DVI cable is longer than 10m.

I downloaded the newest beta driver from www.displaylink.com, simple wizard installation, reboot
and everything works like a charm.

I'm happy with this solution and I will use it further on.

Big thanks to pastrychef and nobodynose.
Thank you guys.