You didn't mention if you have tried any sit-down machines, or if you have experience with FMQ on a domestic. If you've not done either, that would be my first step to recommend.
Like domestic sewing machines and long-arms ... each sit down machine has it's own "feel" to it and the satisfaction rate will vary from user to user. So my second suggestion is to go to a large show and try as many machines as you possibly can. Also note that some machines are oriented horizontally (like a domestic - with the needle to the left and the motor to the right) and some are oriented vertically (needle in the front - motor in the back). Some people will have a preference to how they want to work, and in some cases the set up of your additional tables to accommodate extra quilt bulk may determine that you need horizontal or vertical orientation - so keep that in mind.
I personally have the Juki 2200QVP sit down machine and I do like it. I have had zero mechanical issues with it over 4 years now. Some of the features I like about this machine: The hand wheel is within easy reach from the sitting position which helps when you need to precisely place the needle down in a specific spot, great lighting, large bobbin, vertical orientation (I like the fact that I can't push my quilt back any further than the harp space allows - which means all my extra quilt bulk is to either side of my machine), the extra high harp - greater visibility, excellent speed control, and the best part - the built in bobbin winder (most sit-downs have an external bobbin winder). Things I don't like: the thread cutter (I don't like thread cutters in general), the bobbin can be hard to reach if you have (how to put this gently ...) fat stubby fingers (OK ... not so gentle!!).
Below is a link to a video by Leah Day reviewing the machine.
https://leahday.com/pages/sewing-mac...t-down-longarm