Well, My money's on Starchaser industries.
They may have done a couple of silly things but that was before the X Prize was announced, Now they have proper funding, backing and are test firing of morecambe bay now - This way if one of the rockets goes wrong and destroys the area then it's a bonus
Seriously though, They have test fired rockets well beyond Mach 1, Test fired multi-stage rockets and their plan to put a person into orbit is not overaly ambitious.
They will do it, they will win the X Prize.
Gary.