The Place of Personal Testimony in Evangelism

I do believe that there is a place for testimony. But, evidenced by the continuing errors we make, contemporary American Evangelicalism is post-modern in that (however unintentional) we often replace the objective truths of the gospel, necessary to believe and be saved, with the utter subjectivity of personal testimony. I do believe that personal testimony has its place in the edification of believers, but because of the subjectivity of having ones quality of life improved, or being given the power to obey God's Law to a greater degree, those things really should have a minimal place in an evangelistic situation. The personal testimony that is useful in those cases is if we can point to a time when we once did not believe and repent, and contrast that with the times when we do, thus testifying to the power of God by highlighting His ability to recreate persons who see their sin in contrast to His holiness and believe the gospel. I think a lot of the times we want to substitute transformation for salvation, and this is symptomatic of our mistake of confusing sanctification with justification; confusing Law and Gospel. What eternal good is it if an unregenerate person is inspired in some way by the testimony of my personal transformation, to "change his life" by going to rehab so he can replace bad habits with good ones if he has not first had his heart changed from a heart of stone into a heart of flesh? I'm certain that most Christians would say that it is of no good, and that is the point I'm trying to make--the business of the Kingdom is that of calling persons to see their sinfulness in light of the holiness of God (as reflected in His Law) and to repent of those sins and believe that Christ, in history, lived the perfect life and died the perfect death on a Roman cross, and was raised to glorious life in the place of lowly sinners. Personal transformation (sanctification) will be a result of that continued repentance and belief.