I have a Juki 2010Q that I use just for quilting. It is straight stitch only, (semi industrial), 9 inch harp, auto thread cutter, knee lift, needle threader, adjustable speed control and costs less than a thousand dollars. I could not believe the difference it made in the quality of my FMQ.
I also have a Grace GMQ Pro frame that I will hopefully get set up in the near future to put it on to do frame quilting.
My piecing machine also has a large harp but I only use it for piecing and deco stitches. I've never tried FMQ on it.