I have a Tin Lizzie sit down and comfortably quilted two king sizes already and will be doing my 3rd soon. I also have a Juki 2000 which is a 9" machine. I use that if I need to do anything with a walking foot right now since I have not practiced my ruler work yet on the Lizzie - but even that I only use for small projects. I could not imagine going a huge quilt on my Juki.
There are lots of machines available now - and Juki is coming out with a sit down by spring/early summer next year.
If you ask people which one to get, you'll have a range of replies - mostly for the HQ which I did try but opted to go with the Lizzie and am glad I did.