Not sure on that one. I'm in the same boat as you but the main reason I am considering the upgrade is for better contrast/black levels. I had the RS45 before the HW50 and I've done A/B comparisons in the same room and the difference contrast wise is noticeable so the new JVCs should even be better. in the case of the RS45, the Sony had better motion, better color, better motion interpolation, and RC made the picture sharper but depending on the content the picture would look "cooked" in some cases. From the sound of it though the JVC has caught up with the Sony in these other areas so this is why I am considering one.
Having said that, my viewing is 100% Blu-Ray with a few DVDs. If my main viewing were Live TV/DVR I'm not sure if I would consider the switch if your not viewing a lot of shows with dark scenes.