I have done some FMQ on my own (on my vintage Bernina 830 Record), but enjoyed it much more when I was test-driving Berninas with the BSR.
I purchased a 550QE w/BSR last summer and am practicing on small projects in preparation for doing some larger, "better" quilts.
I have no desire to do embroidery so I didn't consider the other 500 machines, and we full-time in a fifth-wheel, so the 700 and 800 series machines were too big for the space available.
Good luck with your decision.