My 99.5 a4 1.8t qt shakes/wobbles really bad at about 20-25 mph and gets better at higher speeds but still feel the car shake. had the wheels balanced and checked for bent rims. after the balancing same problem. could it be a drive shaft out of balance? bad hub? any help would be appreciated.

 

I doubt the driveline is bent, if you have 4 jack stands get the car on all four.
Dis-able the ESP slowly bring it up to speed while someone is looking at the wheels, i gaurantee you'll find whats making the wobble, or at least pin point which wheel it is.
The truth is most people that balance wheels couldn't fix a light bulb.

 

I have to agree. So much that I would check all the lug bolts and make sure they are tight. Also if you choose to raise it grab the tires and check for play in the suspension.