Hi,
I have an ES300, 2000 model with 150 k miles . i started hearing this clunking noice at about 125 k miles. I have always serviced it with a dealer since 30 k miles. The dealer told me it was the struts and mount. well I changed it and the sound still existed. Then I took it to a local mechanic, he asked me to change the Control ARM and bushings. Since this is an expensive job, i changed some other items such as tie rod and bushings to give a smooth ride. But the Main problem is Control Arm. Clunking noise is gone.
good luck
R