I want to go for a passive system, little bit afraid of headache after a long stay at a 3D monitor. So I selected the LG DM2750D
http://www.lg.com/nl/tv-audio-video/tel ... M2750D.jsp [sorry this is in Dutch]

Now I want to know what Videocard is needed here the AMD HD7970-3Gb or the same priced nVidia GTX680-2Gb

Read somewhere that nVidia can not display 3D on a passive LG???

You can go with either AMD or Nvidia in this case, as you will be using HDMI 1.4a. You can also feed it an interleaved signal directly, for example with iz3D or DDD drivers. I am using a GTX 470 and am able to play just about any game in 3D with medium to high settings (including Battlefield 3).

I'm still figuring out what directions to go, but in the computer store I have noticed that a passive is more friendly to my eyes.
Any chance to test a HD4890 on a LG passive TV??
http://www.sapphiretech.com/presentatio ... id=1&leg=0
http://www.lg.com/nl/tv-audio-video/tel ... LW4500.jsp

just to give it a try before or can this 3d signal not be transported from Vcard to TV because there is no connection on my Vcard for doing that, like new HDMI you mentioned. As you can read on AMD web site AMD HD3d seems not to be supported on this series of Vcards.

AMD HD3D (HDMI 1.4a) won't work on that older card. You can see supported cards here:
http://www.amd.com/us/products/technolo ... ics.aspx#2

However, even with an older card, you may still use a passive display by feeding it a interleaved signal directly (which will work on any kind of video card, even integrated). I know there have been certain issues with this depending on the model TV. This is because sometimes the TV has its own processing of the image that will ruin the interleaved signal. So this won't work 100% of the time. I don't know which specific models are effected though.