I think you will be happy with any black Singer! They are just so well engineered and built! I have two FW's, a 66, 101, 201, and a 15-91. All are great. The 201 is one of my favorites, but I can't FMQ on it because it is a hand crank! But for piecing it is a powerhouse and makes beautiful stitches. My 15-91 is probably my absolute favorite, even above the FW's. The stitching is awesome, it runs quietly, it is powerful, and, best of all, the feed dogs drop and it does beautiful FM quilting!
Just look for a machine that has been well cared for and I don't think you can go wrong! But I would recommend a 201 or 15-91 highly.