I had a very similar problem that gave me fits trying to figure out what was causing it. I balanced all my wheels, changed all of the engine/tranny mounts, and changed both front wheel bearings. Turns out that both of my inner CV joints were bad. They are a pretty weak design IMO.
Here's how to check:
Put your car on an above ground lift, the kind that allows for all 4 of your wheels to hang when it's lifted. Lift the car and have a buddy observe your axles and front wheels while you "drive" the car. Your friend should be able to notice any vibrations in your drive wheels/axles while they are spinning. If your wheels are balanced and your wheels/axles are vibrating you probably have bad axles/inner CV joints.
If it turns out that you've got some bad drive axles, I recommend
www.raxles.com. I bought their upgraded drive axles for about $700 for the set. They come with a full lifetime warrenty and are actually cheaper than buying a set from VW.
