Don, I'll let you know what I know which isn't much...
The 990 is part of Deere's economy line. A big brother to the 790 (though alltogether different). It's made entirely in Japan by yanmar. GST only, like the 790. I sat on one and it's a pretty good sized machine. Impressive specs for the money. A guy at work has one and is happy with it. If the Deere web-site doesn't have details, check JDlawns.com. They had a few specs and pricing listed.
That's all I know, hope it helps /w3tcompact/icons/smile.gif