If you feel the Zeiss Z-plex is to small for you in the field and buy a leupold you should be looking at the heavy duplex rather then the standard. Personally prefer the conquest and swaro a-line's to leupold VXIII in all optical aspects...however I'm not you so buy whichever you feel is the best. Leupold may not be the best for the dollars spent at the present however they are still good optics and a solid choice IMHO.

In regards to the nikon monarch I don't care for the bulk of the 2.5x10x42mm and the power ring is very stiff still after a year on my 10 II ML (which sees a lot of action). Optically I am happy for the dollars, though personally would buy a bushnell elite 4200 instead.

As to which mag (X) I personally don't see the need for more then 10x on a biggame setup. I think the money could be used on better things then more mag on my scope. Just my 2 penny's though.

Good luck