MK do a BB coupler set aswell, that has a single servo pusing both the elevators. It seems to work very well, with little differential in the elevators. CPLR uses it, alomg with countles other people.
I don't think that the high $ setup is needed, aslong as you set it up accurately, with little slop. If you want, you could upgrade the parts at a later stage, if you are not happy with how it flies.
My 2c,
Robert.