I know nobody has mentioned the Wedico cat 966G and I know it has fallen out of favor with a lot of people but Smaulhaul, Scott, has made several nice videos of one pushing and moving dirt. It seems quite impressive in his videos, wish I had one. PMD's price for a 966G kit and all it's gear is right at $7,000!
At first I thought that was a ready to run model but I was wrong.
https://www.youtube.com/watch?v=5QHA60HRh8M
https://www.youtube.com/watch?v=aVWjIZKwbU4