I run my big grizzly at just shy of 400 for turning most the time and just over 200 for threading. Some times I may go up to 700 for cutting my crowns.
Gator chucks are made in China but I've Hurd the guy over them was the man in charge at bison. There some talk on practical machinist that the gators are the same design as the bison and the quality is very good or as good as a bison chuck.
I have the grizzly G509g. The problem you run into with the vfd control is the two speed motor on the lathe. Call vfd direct and ask them about running the two speed motor on a vfd. I ended up with a 15hp American rotory adx