I think it depends on what you're going to use the machine for. What good is a free arm if you don't do any garment sewing? How many hundred fancy stitches does one really need?
I have the 6600 and to be honest, I wish I had gone with a midarm straight stitch machine. I simply do not use 85-90% of the machine's options. It's cool to say I have a fancy machine but at the end of the day I kinda wish I had gone with something with a lot less bells and whistles.