I've used Pfaff for the last 20 years and I love them. I do everything, including king size quilts on them. I machine quilt all my own quilts and I've learned to fmq on them. My favorite for quilting is the Pfaff Expression 2.0, which I got a good buy on 2 years ago when the 4.0 first came out. I dearly love my QE2.
Whatever you decide on, stay away from a light weight machine for fmq. I tried to fmq on my little Brother backup, but it is just too light and I push it all around with the quilt.