There is more to vibration caused by a wheel assembly than balance (you can
balance a square wheel).

Lower profile tires will exagerate a vibration in terms of feeling it in the
car.  That same vibration might have been there but not as noticeable with your
old tires (or you might have just gotten a lousy balance job).  95% of the
public won't notice or care about a less than perfect balance so the sloppy
techs get away with sloppy balance jobs.

I would see if you can find a shop with a Hunter GSP Series Tire Balancer.  It
has a roller that can measure uneven forces in the assembly that are not due to
balance.  The link below has a locator service.

http://www.gsp9700.com/pub/search/findgsp9700.cfm