So many things to consider. Do you have room for a frame longer than 10'? Do you want to quilt larger quilts? Are you planning to quilt as a business? If so I would not get the 10' frame, because there will be times when it will be too small.
What is the throat size of the Fun Quilter? It comes in many different sizes, and with different options. Are you sure it's a good buy? Do you enjoy using your sit-down machine as a sit-down? Do you know much about the frame that you would get with the Sweet Sixteen? (A frame and machine don't necessarily get along unless they were built to be used together.)
Nolting and Handiquilter both have good reputations, but they are not the only longarms available. Have you looked at other options too?
Sorry - no help - just things to think about.