2001 Ford Explorer Front end shake at speed

I noticed a shake before replacing my tires and thought it was from one of them being out of round. I replaced all 4 tires (they were due for it anyway) and thought that would be it. Not even close. It rides smooth as silk until it gets over 60mph. Anything above that and it really begins to wobble. Front end alignment? Done! That was my next step. No changes in how the truck reacts. Worn shocks? Done! Brand new Monroe Sensa-Trac shocks all the way around. Now I am looking at wheel bearings but when I had the truck up and the wheels off to replace the shocks, I did not notice any play in the bearings. What are your ideas for my next thing to try. I had the tires replaced and front end alignment done at our local tread quarters here in Chesapeake, Virginia. They have a pretty good standing with the BBB but I am always looking for a second opinion. Thanks!