Hey Daren, many people on this forum have seen these fighters fight before. ZST posts videos of their events on their web site, which I always make a thread for whenever I see a new one. Go to www.zst.jp and click on Movie.
Morkevicius and Tokoro have become fairly popular because of the ZST web site.
Oishi is a former Shooto champion, and has been around since the mid-90's.
The other 5, however, aren't well known. It's a rather disappointing lineup compared to last year's GP. Katsumura is an extremely exciting grappler, though.