I have the 550 QE and love it. I'm a new sewer and quilter and the BSR is worth the price of the machine.
I've had her now for a year and a half and just took her in for a cleaning, she's hardly stopped working since I got her.
I don't know about other models but the 550 QE is made for quilting and so easy to use. Ofcourse I took the lessons that came with her which I would advise even the best sewer to take, you learn so much about your machine and what it will do. The BSR and walking foot and all the normal feet came with my machine not at an extra cost. I would want this included with the price of the machine and I got a really good deal because of the sale at that time. I'm sure you can deal with whoever you buy from if not go elsewhere.
Good Luck,
Mia