I have the 6600 and love it. Bought it last year, I'm very happy with it. Love the speed control, AccuFeed, thread cutter etc Sews more smoothly than my last Pfaff did. Previously owned 2 Pfaffs, 2 Vikings and a Kenmore (Janome) years ago.
Decided on the 6600 after so many good reviews, and getting great feedback from quilters I know. I know at least 15-20 quilters who have it and love it. My SIL & niece both have one now and love it. It's a heavy duty machine, made to last. IMO Janome gives you a lot for your $$$. Go take a test drive ! :)