Sammy Hagar (ex-Van Halen, Chickenfoot, etc.) has announced that the sixth annual Acoustic-4-A-Cure benefit concert will be held on May 15 at The Fillmore in San Francisco, CA. Joining Hagar at the event will be his The Circle bandmates Michael Anthony (ex-Van Halen, Chickenfoot), Vic Johnson, and Jason Bonham, as well as Tom Johnston (The…