If you are looking for something reliable, and powerful consider the Brother pq1500s. Thread cutter, comes with several feet including quilting and walking, very solid and fast and will definite sew over multiple pieces of fabric without complaint. I think it is now about $700 at Amazon. (It is the same machine as the Babylock Jane which runs quite a bit more - just for the name). The catch - it is only straight stitch. No fancy stitches, not even zig zag. But what it does it does really well and I purchased it because my Viking 870Q with all the bells and whistles had difficulty with freemotion quilting, had to go to the shop regularly, needed more expensive thread (or so I was told) etc. But you do have your Singer for ziq zag etc. Another consideration is servicing. The newer "upscale" machines are sealed so you cannot oil and clean them yourself except for areas right around the bobbin. The PQ1500S allows you to clean and oil (fast and easy) saving you $100 or so at a pop and/or allowing you to keep it maintained more often.
For my money - I would look into the best mechanical machine available. Less fussy, hard working.