If you have conquered FMQ on your Viking on smaller pieces, can you try to make it easier to quilt with it before buying a new machine? When I took the time to make a workable extension covered with slippery vinyl for my sewing cabinet, I had much less struggle with the quilt. I tried both my vintage Bernina 830 Record and Singer 15-91 this way, and ended up preferring the Bernina because it has easier bobbin access.
If I end up buying a new machine for quilting I think I would go with a straight stitch machine like the Babylock Jane or a Juki 2010Q so I could get better lighting, needle down, and thread cutting.