Starting with the 7700 the machines Janome builds for quilters have 11" of harp space. I think the 6600 has 9" and is a nice machine, one of the few that are still made with steel cases.
It is mentioned above but one of the things on the 8900 in the category of why didn't they think of it sooner, is that popup throat plate, easy peasy. For Christmas I'd asked for a short ratchet to make it easier to get those screws off.