I've also been unhappy with left/right TA and have, for now, concluded center of dash really does sound awesome. You also have to remember that the rest of the stage should still "fit" on the dash. If the center is in front of you, instruments played to your left would then have little space left, so that's why it probably muffled the vocals. Also, the manual for my speakers says (and there are) options to change x-over slope and frequency for the tweeters, which I believe changes their on and off axis response. I'll dig it up for more detail. I think sound stage adjustment is not only done via TA, but also with EQ and playing with x-overs. Remember, if you were to disable the driver side tweeter, the stage will almost full shift to the right. This is also where it gets dicey as messing with this can damage the tweeter.