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

If I understand you correctly, you'll use the sheet material to protect the floor while positioning the rack, then you'll remove the protective sheet. If that's the case, how about 1/8" Masonite? It's dense as can be, you shouldn't have any problems rolling over that.

pro flooring installers use a pneumatic lift for moving heavy furniture, its essentially an air bladder that is filled using a compressor and the load slides across the floor on a cushion of air with nary a scuff. I bet you could rent one for an afternoon.

Hi

When we install Master Reference Speakers 520lbs each on casters we bring along 2-3 sheets of 1/8" masonite board to roll them in on - works just great.

Good Luck

Peter

Most large hardware or home improvement stores have disks intended for sliding heavy furniture. They come in different sizes from an inch or so up to six or seven inches diameter. They made from a very hard, slick white plastic that looks almost like teflon. They're flat on the top and slightly curved on the bottom. You tilt up one side of the furniture and put two disks under the legs, then repeat on the other side.

Here's something similar on Amazon.

I think the guys who suggested the Masonite is the way to go. Don't forget the total weight is divided by the number of casters. Assuming you have 4 casters, you'll only have about 165 pounds on each. No problem for 1/8 masonite.