I would say that out the gate a THX calibrator would probably be better (only because I think that they require a higher level of shown competence to get their certificate) I am not THX certified as I thought the expense to do the same thing I do day in day out to get three more initials after my name was way too much..but the facts are that experience is the most important facet in any calibration. THX and ISF calibrators are both trying to achieve the same end result. It is wrong to assume that all ISF or all THX calibrators will be equally competent or able to achieve the same results from your system though. Ultimately no display is perfect and it is up to the calibrator to consider the issues and errors and decide which are the most suitable to be left with in your system.