What do you have your benchtop cnc routers sitting on?

I have ordered a desktop cnc router, about 28 x 28 overall dimensions and 70 pounds. It is made mainly of alluminum. I was planning on just putting it on a flat, sturdy workbench. The machinist, were I work during the day, said it should be on a 300lb "tool" granite top for flatness and stability. That seems a bit extreme to me. Supposedly, the machinist had problems with a similar router being inaccurate on a standard commercial workbench.

What do you guys think?
Have your workbenches/tables caused any problems with cnc routers?

Thanks
Tim

Mine is about the same size and is sitting on 1-1/2" particle board counter top supported by 2" metal legs.

I can't see any problem.

Home Depot has a great workbench they don't advertise, I found them sitting on the 3rd shelf next to the lights. Steel construction, about a 2 inch thick laminated hardwood top, 54 inches long, 2 large ball bearing slide drawers, two shelves, plus freaking large casters for $99. I bought 3 of them!