If you ONLY want a straight stitch, hi-speed, no frills machine for piecing and quilting, here are 5 to look at:
Viking Megaquilter
Janome 1600P
Pfaff Grandquilter
(FYI, all 3 above are the exact same machine made by Janome - just different fronts & labels)
Brother 1500 and Juki 98
If you want size and speed w more stitches and features look at the Janome 6600P - Hi speed, large harp for piecing/ quilting but ALSO has 160 stitches w/ dual feed, speed control, thread cutter, knee control etc :)