GR07 is an incredible deal at its price point and would be appropriate for working out. It has a neutral sound signature, with amazing bass but the treble is not its greatest strength. Still, its almost a no-brainer at this price point. I'd stay away from the SE215 unless you need lots of bass; it got lots of praise when it hit the ground, but quickly was revealed to be a FOTM; they've hat lots of build quality problems. If you use a portable amp, the RE262 is one of my favorite iems and is $149; amazing mids! You may want to do some research on the FXD80; it has some FOTM appeal right now, and I haven't heard it, but it seems like an incredible deal in your price range, if the praise is as good as everyone says.