How do you move a 650lbs Rack on Hardwood...

After reading the various options, I vote for the masonite as the cheapest and safest solution. K.I.S.S.

Others have mentioned it before me.Masonite 1/8 is what you want to use.I've seen it used many times in similar applications or as a floor protector during renovations,remodeling.Just tape it down with red tack tape and roll your rack out on it.
George

Thans to all - I know what I have to do.

Dan

Don't put the masonite directly on the floor! Use heavy rosin type paper of a light moving pad.

My rack doesn't weight quite as much as yours, but it is still a couple hundred pounds, loaded. I do not use casters but points. I have the discs that the points go into and felt adhered to the bottom of the discs. These allow my whole rack to slide nicely on my wood floor, especially if you are sliding with the orientation of the wood (not grain, but how it is laid).