I love my EX-21. Some things to look at:
Have you seen and used this one yourself? (feel for vibration or wobble, listen for noise)
Can you pick it up locally (no need to ship it)?
Does it include the stand?
Is the table top free of any scratches?
Is the blade perpendicular to the table when your set the tilt to zero using the tilt index button?
Is there a foot switch?
Is there a work light?
If all 7 answers are "yes" then $600 seems like a good deal. I'd deduct some $$$ for each one that is not a "yes".