I have the 6600, purchased it used last month. So far I like it. I agree putting together a list of must haves and then wants. While you are there try some other machines and other brands if the shop has them. Anyone who sews can sew on any working machine but we will all have machines we bond with and find easier to use.
I’m confused about the comments about it being expensive? While spending $1,100 is a lot of money for a sewing machine it is not a lot for THAT sewing machine. I have been watching Ebay for the last few months and the least amount the 6600 have sold for was about $850(that was only 1) most have been selling for $900-$1,300 and those are from unknown entities so you are taking a bigger risk. I purchased my 6600 on Ebay, with a great table as my closest dealer is almost a 2 hour drive and she did not have any used/show models.