Thank you Mea for taking the time to respond. You've confirmed some differences that I had suspected as well. I went ahead and ordered the MOD 100Q from Costco as it looks like it is just missing the thread cutter and the presser foot pressure adjustment. I have the the thread cutter on my 6600 that I rarely use, so don't think I'll miss it and the only thing I'm left wondering about is the necessity of the presser foot adjustment, when I'm only likely to use this machine for piecing quilting cotton. Years ago we bought our daughter a Kenmore branded/Janome made sewing machine which does not have a presser foot adjustment and she has been sewing garments with her machine quite successfully, so I have to think its not going to be an issue. Apparently Costco only brings in these machines at this time of the year and this year they are priced at $400, so it seems like a good deal to me!