First the vibration....The first thing to suspect is the wheel balance. Since that didnt work, the next thing to suspect is that one or more of the tires are out of round, or have tread defects. The best thing to do is to try and isolate the problem, since odds are that all 4 are not problematic. Rotate the front left to the rear left, and test drive. Then the right. I've located many a problem this way. Oft times, if the problem is in the left front, for instance, when you rotate it to the back, the problem will appear to go away, because the steering wheel involvement is most closely associated with a front wheel problem. For the wheel in the back to cause a problem, it would have to be really out of round..enough so that you would not feel it in the steering wheel, but in the body of the car as it 'bounces' along.

Re the sway bars, when I had mine done at my Volvo dealer, they said that re-aligning was NOT necessary...This is confirmed by the Haynes manual. But , particularly in the rear, a certain procedure for marking the suspension components must be followed so that they are put back properly, otherwise the rear WILL be out of Toe.