I went to the Cincinnati Quilt Show last year and tried every one there - about 8 or 10. I shook every frame and tried each machine on both days of the show. I realized that the frame is important too.
I ended up getting a Baby lock Crown Jewel with a Grace Majestic frame. I am very happy with both. The Jewel was very smooth. One of the best things was the 4 day class in St. Louis that was included in the deal and the 0% interest loan which I have already partially paid off now. The HQ Avante is the same 18" arm machine as the jewel but the frame they give you is different. I have a friend who has that but I don't like her frame as well. She also did not get much help in using it although they did spend a day with her setting it up and teaching her some.
The big issue is the space that you may have. Mine is a 10 foot frame and fits well in my 15 foot wide sewing room. I can do a large queen or a small king on it but not a large king as you cannot quilt all the way to the edges of the frame. The 12 foot frame would not fit well in the room.
I have had no problems with the 18 inch arm length. Have been able to do everything I needed on it easilly.
Good luck in your looking. Hope you find something that is as much fun as I have had.