Brother 1500 S has a nice size throat space and does FMQ well. It's a straight stitch only, mechanical machine that you can pick up brand new for $600 including an extension table, walking foot, FMQ foot, 1/4 inch foot and a couple of others. Many folks on the board have them set up on a frame. I use mine every day for all kinds of sewing and love it.
Of course, you will get 1000 suggestions. It's like the Ford vs. Chevy debate. Everyone has an opinion but both are nice vehicles.