I've decided against an upper level with a loop. I believe it will mess up a nice little layout. I made this decision after testing my three locomotives. It was hard for me to believe that after the layout was laid up against the wall behind the couch for six months, that it actually ran so perfectly after a light cleaning. Here is a brief video of the testing session.
So, my new plan is to add track here. After pulling the layout away from the wall 7"... it looks like I'll have enough room for a couple of sidings. My stationary decoder only has ports for two more switch machines, so I am limited to two new turnouts. These are my choices for the new configuration so far.