I agree with others----skip the 7700 as the updates on the newer ones are well worth it. The 8200 is what I have and yes, hands down, absolutely, 100% worth the extra throat space over a 6600 or 6500, plus it has the free arm which is a must for something like sleeves, hems, etc.
Think about whether you want to wrestle a quilt through 6" throat space or 11" . It's a no-brainer if you can swing it financially. You won't regret it for a second.
My 8200 is quiet, fast, has more stitches than I can use (but I have played with them all), multiple button hole options (none of which I've used because I'm not a garment sewer, but I would like to experiment someday). I've never had to change the needle plate. Doing FMQ on it is a dream. The auto tension is perfect--never had trouble with it. THe auto thread cutter is something I'd have a hard time doing witout now. Love that. It has a knee lift I've never used but am about to experiment. Can't say enough good about it.
See if you can find a "rebox"--one that was returned by a customer if you can, used just a few hours, or a floor model sale. I got a rebox that was a fabulous price--only $200 bucks more than I was finding for a very used 7700.