I'm looking to buy a scope to put on my new rifle for an upcoming antelope hunt. I would like to extend my range out to 600 yards max. I'm torn between getting a nikon monarch 4-16 x 42 or the 5-20 x 44 model. Is 16x enough power? or should I go with the 20x? I currently own a 3-9x scope and deer past 300 yards look small. I just want to make sure I have enough power to make the longer shots. Which one would you go with??