I don't have a sit down model but I do have the Tin Lizzie 18LS. I almost bought the Queen Quilter, the only difference is the 18LS has the Stitch Regulator. You will definately want to have that.
Make sure your dealer is local. I am having an issue today and even with the dealer being local, I have to take my machine in and wait 2 days for them to fix it. I couldn't imagine having to get it someplace far away on top of the frustration of having my machine down.