CMS Functionality in existing site

I have an existing website template where I need a solution for posting and editing news as well as a forum for users. The website is based on + C# and I already load my content pages dynamically as well as have a login user section for members.
What I need is advice on a news / forum solution I can add into the site (call to my template). I don’t need a full CMS only the news and forum parts and need to match it to my existing design.
So far the solutions I’ve looked at are vbulletin, wordpress and umbraco.

Or is it going to be better to write my own new script and just integrate a forum like phpbb?

I am assuming this means the site is written in ASP. In that case you need to talk to your host, only the newest version of IIS can run PHP. WordPress, phpBB, and vBulletin are PHP-based, I never worked with umbraco so I cannot comment on that.

try there are many other .net cms around as well.