The main benefit of going prior to the summer after Junior year would be for the experience. Not just the experience of a showcase/camp which you can get any where, but the experience of talking to college coaches. This is invaluable and you won't get it at a lot of other places.
My son went after his freshman year and again after his junior year. There was a coach there who remembered him from his earlier visit and ended up inviting him for a campus visit.
Making contact with the coaches prior to attending Headfirst is an excellent idea. This way they already have an idea of who you are when you introduce yourself to them. My son was walking the grounds between games and a coach came up to him and addressed him by name. The coach said he recognized my son from the picture on his athletic profile that he was sent.
The important thing to remember is to be proactive in talking to the college coaches. Go up to them and introduce yourself. Don't wait for them to find you. There wasn't one college coach who wouldn't give my son a few minutes of his time when he attended as an undeclassman.