http://www.matrix28.com/ Fluid design works well when the site has a lot of content like news, articles, maybe blog, and BBS. I suppose you have a lot of content but not a whole lot of writings. I don't know if fluid design best suites your site.
http://www.computerforums.org/ Not too many comments actually. This is almost like a plain installation of vBulletin. The forum looks pretty active and if you are happy about it, then I guess you can try to moderate the forum and get more active members. If you want to really grow the community, perhaps you can start posting articles, news, and so forth. Create content, you know?