A good mid-priced all around binding would be the Mission. If you want more response get the Cartels.
Get the Malavitas if you're more park oriented. I can't necessarily speak for K2, but their quality looked cheap when I saw them at the store. I can definitely speak for Rome: I had a pair of 390's and they were garbage. Cheap plastic spacers in their design (who does that?), horrible unresponsive metal heel loop, poor boot size fit, and cheap foam straps and buckes, etc. I don't think I'll even go back to Rome bindings.
I also can't really speak for Union, but I personally don't like their poorly designed toe straps.