How big of lens you want becomes an issue of how much weight and how much money your willing to deal with. I do know you'll be better off to spend extra money on quality lenses...not just bigger lenses. 50mm is not NEEDED for night hunting (but you may look at a lighted reticle or bushnells "firefly" series)

X14.5 is WAAY enough for 200yard yotes (don't worry I won't say its overkill though)