Have to say I love, love, love my Singer 15-91! Straight stitch only, mine has reverse. I have pieced/quilted a king sized quilt on it. It does not have an auto-threader or thread cutter (which is really important to some) - but I don't mind. I find her relaxing to sew on, and I absolutely love how it feels when I FMQ on her.
I also have a Janome MC4800 (have had for about 8 years now). I use her occasionally, but prefer my Singer.
Additionally, I have a Singer 401 that I like as well. I have to replace a plug on her that I messed up, so haven't been able to use her for a bit.
Good luck in your search - lots of great ideas of what to look at here!