50C? All depends but i doubt that under orthos x2 it will stay under 50C. Maybe you if you got a lucky chip lol. Why do you want it to be under 50C? Anything under 60C is completely safe.
I currently have a thermalright 120 extreme w/ a scythe s-flex fan. The 120 extreme doesnt come with a fan so price/performance I would say the Ninja wins. Still even thought it costs more I would recommend the 120 extreme if your looking for the best possible air cooling your can get.