I also found a great used 6600 and love it. I use the accufeed walking foot system as often as I can....works wonderful and so easy to use. I have the 1/4" foot but had to adjust the needle to the right to get a true 1/4". It also came with the SITD foot and it's ok, but to me it didn't make much difference. I don't use the knee lifter, seems to be more of a bother and in the way. Mine came with an extension table, but I never use it....bought the table made to fit it. I will never regret the purchase, she does everything I ask of her and more.