Carpet squares is a great idea! Definitely stay away from the interlocking rubber type. They are cheaper, but they also tend to be excellent generators of static electricity, which is bad news for electronics.
When I did the floor in my train room my employer was renovating offices. I talked with the contractor and was able to get all I needed and more to redo my room free of charge. The squares were in practically brand new condition, and I was able to keep them from going to a land fill. Win-win in my book! Ask around. You may get lucky!
Chris
LVHR
