Never played any of the Wizardry games, but I have to admit, Wizardry 8 looks very intriguing. Definetly want to try it, even if it is very difficult. So I was wondering, how importat (story wise) it is to play W6 and W7 before W8? As far as I understand Wizardry 6 - 8 is a trilogy and W8 finishes that trilogy. Do I lose something importat if I start directly at W8?

You can do one of two (or both) things: Wiz 6 - 8 allow you to carry party members over through character saves, so either buy 6 & 7 and play them them, importing files through each game, and then play 8 and import the characters from 7 into 8. OR, just play 8 with a created party or one made up of default characters and ones you make (or any combination of the two).

In terms of story, depending on how you ended Wiz 7, the beginning area of Wiz 7 will be different or you'll get a different opening movie at the beginning of a new game.

Flip a coin and choose - either way, you'll have a really good time...

Yes you can just start from 8;
In wiz 7 you have three basic endings which carry over into eight,
1. side with the rhinos,
2. side with the bugs,
& 3. side with the main villain.
Theses ending have a minor difference on starting location and some special items (zap gun and music instruments) which are nice to have but not game braking.
Imo a new player is better starting in wiz8 because that game has the best balance (both story and game mechanics) for the first play through.

Edit: my old wiz7 end-game save.

Not only you can,
But if it is your first time playing a game such as these, you also should.
Wiz 8 has the most accessible interface and control scheme. I has a lot of possibilities, varied scenery, and it's the most well rounded for newbies (I also started with wiz 8 first, then tried earler installments).
Wiz 6 might seem incredibly dated by today's standards. Even back in the day it was a game for the "hardcore" crowd. You're locked in a dungeon, there's no automap, and everything is stronger than you (though, still a step back in difficulty compared to the first 5 games which were plain evil). Wiz 7 might seem more accessible, but still, very-very hard and unforgiving (at least the world opens up significantly).
The real reason to play though the trilogy is that you can import characters from 5 to 6 and from 6 to 7.
The guys at Sir-tech added different starting and ending tidbits for players who made through the whole ordeal, which is nice, but not all that neccesary to enjoy wiz8 alone.
Also, I beleive it must be one heck of an accomplishent to finish these in order, but that's something even I never managed to do :)

I'd jump right in with Wizardy 8 and enjoy it.

Yeah, my first experience was with Wizardry 8, which I loved so much I've tried to track down every entry in the series since (including the Japanese games, some of which were pretty good, though more in the vein of the very early Wizardry games than 6-8).
While the story is continuous between Wizardry 6, 7 and 8, Wizardry 8 does explain the back story both in the intro and with the interactions with recurring NPC's, so you get a pretty good grasp of what's happening.

Thanks alot for the info. I'll jump right on it. And I have whole weekend to figure the game out... :)