The benefits of becoming a supporting member of iRV2 are listed in the OP, here:
http://www.irv2.com/forums/f62/irv2-...rs-113379.html
What "announcements" are you describing?
Each Forum and sub-Forum has a short number of "Stickies". The staff prevents too many within any Forum. The Stickies are not removable.
If you would like to "Subscribe" to a Forum, only threads with new content will be listed when you view your subscriptions on your "User CP" (button at the top left of any page).
Best luck